research article iodine-mediated neutral and...
TRANSCRIPT
Hindawi Publishing CorporationJournal of ChemistryVolume 2013 Article ID 916960 5 pageshttpdxdoiorg1011552013916960
Research ArticleIodine-Mediated Neutral and Selective N-Boc Deprotection
G Pavan Kumar1 D Rambabu2 M V Basaveswara Rao3 and Manojit Pal2
1 Department of Chemistry Acharya Nagarjuna University Guntur Andhra Pradesh 522510 India2Dr Reddyrsquos Institute of Life Science University of Hyderabad Campus Hyderabad 500046 India3 Department of Chemistry Krishna University Machilipatnam Andhra Pradesh 521001 India
Correspondence should be addressed to Manojit Pal manojitpalrediffmailcom
Received 6 May 2013 Accepted 17 June 2013
Academic Editor Hakan Arslan
Copyright copy 2013 G Pavan Kumar et alThis is an open access article distributed under theCreativeCommonsAttribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
A simple efficient and alternative method has been developed for theN-Boc deprotection of structurally diverse protected aminesSelective removal of N-Boc groups was achieved with excellent yields under a solvent-free condition or in a solvent using iodineas a catalyst The methodology involving the first use of iodine for N-Boc deprotection of protected amines represents an effectiveand useful alternative to the previously reported methods
1 Introduction
Amine is one of the commonly used functionalities in syn-thetic organic chemistry and its protection in the form ofan N-tert-butoxycarbonyl (N-Boc) derivative has become aregular strategy in the synthesis of complex natural productspeptides or small organic molecules [1] The key advantagesof Boc group include its ease of installation and stabilitytowards various nucleophiles including strong basic con-ditions in a number of chemical transformations [2ndash4]Traditional methods for Boc-protection involve the reactionof amines with di-tert-butyl dicarbonate (Boc)
2O in the
presence of 4-(NN-dimethylamino) pyridine (DMAP) [5] orinorganic bases [6] Several strategies have been developedfor the N-Boc deprotection earlier A variety of reagentshave been employed to effect this transformation includingstrong acids Lewis acids and neutral conditions assistedby microware Thus N-Boc deprotection has been carriedout successfully using mild acidic conditions [7] such as tri-fluoroacetic acid (TFA) HCl H
2SO4 aqueous phosphoric
acid [8] or Lewis acids such as BF3sdotOEt2 TMSI TMSOTf
TiCl4 SnCl
4 AlCl
3 Sn(OTf)
2 and ZnBr
2[9] The use of
montmorillonite K10 clay catalyst [10] and silica gel [11] orthermolytic conditions at high temperature [12 13] have alsoshown to work Cleavage of the Boc group can be achievedin some cases under basic conditions where the amine isactivated such as pyrroles [14ndash16] Microware-assisted N-Boc deprotection under mild conditions using K
3PO4sdotH2O
in CH3OH has been reported [17] A catalyst-free N-Boc
deprotection has been reported in subcritical water underpressure [18] Recently severalN-Boc derivatives of aromaticamines and amino acids were deprotected in boiling water[19] While many of these methods are quite elegant andeffective a few number of them however suffer from draw-backs such as (i) longer reaction time (ii) high temperature(iii) low yield of products and (iv) the use of expensivecatalysts Moreover preparation of some of the catalystsrequires cumbersome procedures As an inexpensive andreadily available reagent iodine has attracted considerableinterest due to its less hazardous nature and efficiency invarious organic transformations [20] Herein we report ourpreliminary results of newly found iodine-mediated N-Bocdeprotection of various protected amines under a mild andsolvent-free condition
2 Experimental
21 GeneralMethod for N-BocDeprotection of 1 Amixture ofN-Boc protected amine 1 (10mmol) and iodine (008mmol)was grinded in a mortar for the time indicated in Table 2After completion of the reaction (indicated by TLC) themixture was diluted with CH
2Cl2(10mL) and washed with
saturated aqueous solution of sodium thiosulphate (2times 5mL)and then with saturated aqueous solution of NaCl (2 times5mL) The organic layer was collected dried over anhydrousNa2SO4 and filtered and concentrated under low vacuum
2 Journal of Chemistry
Table 1 Effect of solvents on iodine-mediated de-N-tert-butoxy-carbonylation of N-Boc-aniline (1a)a
HN
O
O
I2rt solvent
NH2
1a 2a
Entry Solvent Time Yieldb ()1 DCM 5h 942 CH3CN 6h 923 Benzene 9 h 884 Toluene 12 h 825 No solvent 30min 98aAll the reactions were carried out using the tert-butyl phenylcarbamate (1a10mmol) and iodine (008mmol) at room temperaturebIsolated yield
The residuewas purified by column chromatography to affordthe pure products 2andasho
3 Results and Discussion
In our initial study tert-butyl phenylcarbamate (1a) wasreacted with 8mol of iodine at room temperature in arange of organic solvents separately Results of this studyare summarized in Table 1 A number of solvents suchas DCM CH
3CN benzene and toluene were examined
(Table 1 entries 1ndash4) when the deprotected aniline (2a) wasisolated in good yield
While the duration of the reaction was 5ndash12 h in all thesecases in the absence of a solvent the reaction was completedwithin 30min affording the desired product in 98 yield(Table 1 entry 5)These observations encouraged us to exam-ine the generality and scope of this method Accordinglya variety of aliphatic and aromatic N-tert butylcarbamates(2) were treated with iodine under a solvent free conditionwhen the corresponding amine (1) was isolated in good yield(Table 2) A variety of aryl (entries 1ndash9 Table 2) heteroaryl(entries 11ndash14 Table 2) and aliphatic amines (entries 10 and15 Table 2) were deprotected following this methodologyWe have also examined all these reactions in DCM andthe desired amines were isolated in good yields (Table 2)Notably the present iodine-mediated N-Boc deprotectionwas found to be a slower process than the iodine-mediatedN-Boc protection [21] perhaps due to the higher stability ofthe N-tert butylcarbamate moiety of 2 than the ndashOCOOtBugroup of Boc
2O towards elemental iodine
A plausible mechanism for iodine catalyzed N-depro-tection of 1 is presented in Scheme 2The reaction seemed toproceed via activation of the carbonyl oxygen of 1 by iodineleading to E-1 which underwent the sequential cleavageof several bonds such as CndashH CndashO and CndashN bond Theinteraction of molecular iodine with carbonyl oxygen hasbeen described in the literature earlier [21 22] For example
N
O
O
21
rt 30ndash240 min(no solvent)
R
R998400
NR
R998400
HI2
Scheme 1 Iodine-mediated N-Boc deprotection of amines undersolvent-free conditions
1I2 X
X
HN
HN
O
O
O
O
CH3
CH3
CH3
CH3
I+
I+
Iminus
Iminus
HCH2
H3C
I2 + CO2
2
E-1
+ CH2=C(CH3)2
Scheme 2 Proposed mechanism for iodine catalyzedN-Boc depro-tection of 1
nucleophilic addition of indole to a carbonyl compound wascatalyzed efficiently by molecular iodine [23] It was sug-gested that a halogen bond [defined as intermolecular non-covalent interaction between halogen atom and electron-donor atom such as O or N (similar to hydrogen bond)] [24]between the carbonyl oxygen and iodine molecule plays akey role in the catalytic effect of iodine observed in thesereactions [25] Nevertheless the cleavage of CndashH of the tBugroup perhaps was facilitated by the iodine coordinated withthe carbonyl oxygen As a result the catalyst iodine wasregenerated along with the extrusion of carbon dioxide and2-methylpropene affording the desired amine 2
4 Conclusions
In conclusion we have developed a simple efficient andalternativemethod for theN-Boc deprotection of structurallydiverse protected amines The selective removal of N-Bocgroups was achieved with excellent yields under a solventfree condition using iodine as a catalyst To the best of ourknowledge this is the first example of N-Boc deprotection ofprotected amines catalyzed by elemental iodine The presentdeprotection methodology has potential to become an effec-tive and useful alternative to the previously reportedmethodsand may find applications in protecting group chemistry
Acknowledgments
The authors thank the management of Acharya NagarjunaUniversity andDr Reddyrsquos Institute of Life Science for contin-uous encouragement and support
Journal of Chemistry 3
Table 2 Iodine-mediated deprotection of N-tert butylcarbamates (1) (Scheme 1)
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
1
NHBoc
1a 30
NH2
2a 98 94
2 1b
NHBoc
F50
NH2
2bF
90 82
3 1c
NHBoc
Cl90
NH2
2cCl
92 80
4 1d
NHBoc
Br120
NH2
2dBr
90 80
5 1e
NHBoc
CH3
90
NH2
2eCH3
82 80
6 1f
NHBoc
OH120
NH2
2fOH
90 85
7
NHBoc
1g
OH
H3C150
NH2
2g
OH
H3C86 80
4 Journal of Chemistry
Table 2 Continued
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
8
NHBoc
1hOCH3
60
NH2
2hOCH3
92 85
9
NHBoc
1iNO2
120
NH2
2iNO2
90 85
10
NHBoc
1j 90
NH2
2j 82 78
11
NBoc
1k 100
NH
2k 85 80
12
NBoc
1l
CHO
150
NH
2l
CHO
82 76
13
NBoc
1m
O
180
NH
2m
O
80 72
14
NBoc
1n
COOEt
240
NH
2n
COOEt
86 80
15
NBoc1o
O
120
NH2o
O
84 78aAll the reactions were carried out using the N-tert butylcarbamate 1 (10mmol) and iodine (008mmol) at room temperature
bIsolated yieldcAll the reactions were carried out using DCM (5mL) at room temperature for 5-6 h
References[1] G Sartori R Ballini F Bigi G Bosica R Maggi and P Righi
ldquoProtection (and deprotection) of functional groups in organicsynthesis by heterogeneous catalysisrdquo Chemical Reviews vol104 no 1 pp 199ndash250 2004
[2] E Gross and JMeienhoferThePeptides vol 3 Academic PressNew York NY USA 1981
[3] P J Kocienski Protecting Groups vol 185 chapter 6 Thieme-Stuttgart 1994
[4] G Theodoridis ldquoNitrogen protecting groups recent develop-ments and new applicationsrdquo Tetrahedron vol 56 no 16 pp2339ndash2358 2000
[5] Y Basel andAHassner ldquoDi-tert-butyl dicarbonate and 4-(dim-ethylamino)pyridine revisited Their reactions with amines
Journal of Chemistry 5
and alcoholsrdquo Journal of Organic Chemistry vol 65 no 20 pp6368ndash6380 2000
[6] S T Handy J J Sabatini Y Zhang and I Vulfova ldquoProtectionof poorly nucleophilic pyrrolesrdquoTetrahedron Letters vol 45 no26 pp 5057ndash5060 2004
[7] P G M Wuts and T W Greene Greenersquos Protective Group inOrganic Synthesis JohnWily and Sons NewYork NY USA 4thedition 2007
[8] B Li R Bemish R A Buzon et al ldquoAqueous phosphoric acid asa mild reagent for deprotection of the t-butoxycarbonyl grouprdquoTetrahedron Letters vol 44 no 44 pp 8113ndash8115 2003
[9] D S Bose K K Kumar and A V N Reddy ldquoA new protocolfor selective deprotection of N-tert-butoxycarbonyl protectivegroup (t-Boc) with Sn(OTf)
2rdquo Synthetic Communications vol
33 no 3 pp 445ndash450 2003[10] N S Shaikh A S Gajare V H Deshpande and A V Bedekar
ldquoAmild procedure for the clay catalyzed selective removal of thetert- butoxycarbonyl protecting group from aromatic aminesrdquoTetrahedron Letters vol 41 no 3 pp 385ndash387 2000
[11] T Apelqvist and D Wensbo ldquoSelective removal of the N-Bocprotective group using silica gel at low pressurerdquo TetrahedronLetters vol 37 no 9 pp 1471ndash1472 1996
[12] V H Rawal R J Jones and M P Cava ldquoPhotocyclizationstrategy for the synthesis of antitumor agent CC-1065 synthesisof dideoxy PDE-I and PDE-II Synthesis of thiophene and furananalogues of dideoxy PDE-I and PDE-IIrdquo Journal of OrganicChemistry vol 52 no 1 pp 19ndash28 1987
[13] K Nadia B Malika K Nawel B MedYazid R Zine and N-EAouf ldquoSimple and efficient cleavage reaction of the Boc groupin heterocyclic compoundsrdquo Journal of Heterocyclic Chemistryvol 41 no 1 pp 57ndash60 2004
[14] I Hasan E R Marinelli L-C C Lin F W Fowler and AB Levy ldquoSynthesis and reactions of N-protected 2-lithiatedpyrroles and indoles The tert-butoxycarbonyl substituent as aprotecting grouprdquo Journal of Organic Chemistry vol 46 no 1pp 157ndash164 1981
[15] S El Kazzouli J Koubachi S Berteina-Raboin A Mouaddiband G Guillaumet ldquoAmild and selective method for the N-Bocdeprotection by sodium carbonaterdquo Tetrahedron Letters vol 47no 48 pp 8575ndash8577 2006
[16] N J Tom W M Simon H N Frost and M EwingldquoDeprotection of a primary Boc group under basic conditionsrdquoTetrahedron Letters vol 45 no 5 pp 905ndash906 2004
[17] S R Dandepally and A L Williams ldquoMicrowave-assistedN-Boc deprotection under mild basic conditions usingK3PO4sdotH2O in MeOHrdquo Tetrahedron Letters vol 50 no 9 pp
1071ndash1074 2009[18] GWang C Li J Li and X S Jia ldquoCatalyst-free water-mediated
N-Boc deprotectionrdquo Tetrahedron Letters vol 50 no 13 pp1438ndash1440 2009
[19] JWang Y-L Liang and J Qu ldquoBoiling water-catalyzed neutraland selective N-Boc deprotectionrdquo Chemical Communicationsno 34 pp 5144ndash5146 2009
[20] J S Yadav B V Subba Reddy K Premalatha and T SwamyldquoFirst example of the activation of polymethylhydrosiloxanewith molecular iodine a facile synthesis of 36-dihydropyranderivativesrdquo Tetrahedron Letters vol 46 no 15 pp 2687ndash26902005
[21] R Varala S Nuvula and S R Adapa ldquoMolecular iodine-cata-lyzed facile procedure for N-Boc protection of aminesrdquo Journalof Organic Chemistry vol 71 no 21 pp 8283ndash8286 2006
[22] Y-H Wang L Li and X-S Chen ldquoTheoretical studies on theiodine-catalyzed nucleophilic addition of acetone with five-membered heterocyclesrdquo Chemical Research in Chinese Univer-sities vol 24 no 4 pp 520ndash524 2008
[23] B P Bandgar and K A Shaikh ldquoMolecular iodine-catalyzedefficient and highly rapid synthesis of bis(indolyl)methanesunder mild conditionsrdquo Tetrahedron Letters vol 44 no 9 pp1959ndash1961 2003
[24] A C Legon ldquoPrereactive complexes of dihalogens XY withLewis bases B in the gas phase a systematic case for the halogenanalogue Bsdot sdot sdotXY of the hydrogen bond Bsdot sdot sdotHXrdquo AngewandteChemie vol 38 no 18 pp 2686ndash2714 1999
[25] G R Desiraju and R L Harlow ldquoCyano-halogen interactionsand their role in the crystal structures of the 4-halobenzoni-trilesrdquo Journal of the American Chemical Society vol 111 no 17pp 6757ndash6764 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
2 Journal of Chemistry
Table 1 Effect of solvents on iodine-mediated de-N-tert-butoxy-carbonylation of N-Boc-aniline (1a)a
HN
O
O
I2rt solvent
NH2
1a 2a
Entry Solvent Time Yieldb ()1 DCM 5h 942 CH3CN 6h 923 Benzene 9 h 884 Toluene 12 h 825 No solvent 30min 98aAll the reactions were carried out using the tert-butyl phenylcarbamate (1a10mmol) and iodine (008mmol) at room temperaturebIsolated yield
The residuewas purified by column chromatography to affordthe pure products 2andasho
3 Results and Discussion
In our initial study tert-butyl phenylcarbamate (1a) wasreacted with 8mol of iodine at room temperature in arange of organic solvents separately Results of this studyare summarized in Table 1 A number of solvents suchas DCM CH
3CN benzene and toluene were examined
(Table 1 entries 1ndash4) when the deprotected aniline (2a) wasisolated in good yield
While the duration of the reaction was 5ndash12 h in all thesecases in the absence of a solvent the reaction was completedwithin 30min affording the desired product in 98 yield(Table 1 entry 5)These observations encouraged us to exam-ine the generality and scope of this method Accordinglya variety of aliphatic and aromatic N-tert butylcarbamates(2) were treated with iodine under a solvent free conditionwhen the corresponding amine (1) was isolated in good yield(Table 2) A variety of aryl (entries 1ndash9 Table 2) heteroaryl(entries 11ndash14 Table 2) and aliphatic amines (entries 10 and15 Table 2) were deprotected following this methodologyWe have also examined all these reactions in DCM andthe desired amines were isolated in good yields (Table 2)Notably the present iodine-mediated N-Boc deprotectionwas found to be a slower process than the iodine-mediatedN-Boc protection [21] perhaps due to the higher stability ofthe N-tert butylcarbamate moiety of 2 than the ndashOCOOtBugroup of Boc
2O towards elemental iodine
A plausible mechanism for iodine catalyzed N-depro-tection of 1 is presented in Scheme 2The reaction seemed toproceed via activation of the carbonyl oxygen of 1 by iodineleading to E-1 which underwent the sequential cleavageof several bonds such as CndashH CndashO and CndashN bond Theinteraction of molecular iodine with carbonyl oxygen hasbeen described in the literature earlier [21 22] For example
N
O
O
21
rt 30ndash240 min(no solvent)
R
R998400
NR
R998400
HI2
Scheme 1 Iodine-mediated N-Boc deprotection of amines undersolvent-free conditions
1I2 X
X
HN
HN
O
O
O
O
CH3
CH3
CH3
CH3
I+
I+
Iminus
Iminus
HCH2
H3C
I2 + CO2
2
E-1
+ CH2=C(CH3)2
Scheme 2 Proposed mechanism for iodine catalyzedN-Boc depro-tection of 1
nucleophilic addition of indole to a carbonyl compound wascatalyzed efficiently by molecular iodine [23] It was sug-gested that a halogen bond [defined as intermolecular non-covalent interaction between halogen atom and electron-donor atom such as O or N (similar to hydrogen bond)] [24]between the carbonyl oxygen and iodine molecule plays akey role in the catalytic effect of iodine observed in thesereactions [25] Nevertheless the cleavage of CndashH of the tBugroup perhaps was facilitated by the iodine coordinated withthe carbonyl oxygen As a result the catalyst iodine wasregenerated along with the extrusion of carbon dioxide and2-methylpropene affording the desired amine 2
4 Conclusions
In conclusion we have developed a simple efficient andalternativemethod for theN-Boc deprotection of structurallydiverse protected amines The selective removal of N-Bocgroups was achieved with excellent yields under a solventfree condition using iodine as a catalyst To the best of ourknowledge this is the first example of N-Boc deprotection ofprotected amines catalyzed by elemental iodine The presentdeprotection methodology has potential to become an effec-tive and useful alternative to the previously reportedmethodsand may find applications in protecting group chemistry
Acknowledgments
The authors thank the management of Acharya NagarjunaUniversity andDr Reddyrsquos Institute of Life Science for contin-uous encouragement and support
Journal of Chemistry 3
Table 2 Iodine-mediated deprotection of N-tert butylcarbamates (1) (Scheme 1)
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
1
NHBoc
1a 30
NH2
2a 98 94
2 1b
NHBoc
F50
NH2
2bF
90 82
3 1c
NHBoc
Cl90
NH2
2cCl
92 80
4 1d
NHBoc
Br120
NH2
2dBr
90 80
5 1e
NHBoc
CH3
90
NH2
2eCH3
82 80
6 1f
NHBoc
OH120
NH2
2fOH
90 85
7
NHBoc
1g
OH
H3C150
NH2
2g
OH
H3C86 80
4 Journal of Chemistry
Table 2 Continued
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
8
NHBoc
1hOCH3
60
NH2
2hOCH3
92 85
9
NHBoc
1iNO2
120
NH2
2iNO2
90 85
10
NHBoc
1j 90
NH2
2j 82 78
11
NBoc
1k 100
NH
2k 85 80
12
NBoc
1l
CHO
150
NH
2l
CHO
82 76
13
NBoc
1m
O
180
NH
2m
O
80 72
14
NBoc
1n
COOEt
240
NH
2n
COOEt
86 80
15
NBoc1o
O
120
NH2o
O
84 78aAll the reactions were carried out using the N-tert butylcarbamate 1 (10mmol) and iodine (008mmol) at room temperature
bIsolated yieldcAll the reactions were carried out using DCM (5mL) at room temperature for 5-6 h
References[1] G Sartori R Ballini F Bigi G Bosica R Maggi and P Righi
ldquoProtection (and deprotection) of functional groups in organicsynthesis by heterogeneous catalysisrdquo Chemical Reviews vol104 no 1 pp 199ndash250 2004
[2] E Gross and JMeienhoferThePeptides vol 3 Academic PressNew York NY USA 1981
[3] P J Kocienski Protecting Groups vol 185 chapter 6 Thieme-Stuttgart 1994
[4] G Theodoridis ldquoNitrogen protecting groups recent develop-ments and new applicationsrdquo Tetrahedron vol 56 no 16 pp2339ndash2358 2000
[5] Y Basel andAHassner ldquoDi-tert-butyl dicarbonate and 4-(dim-ethylamino)pyridine revisited Their reactions with amines
Journal of Chemistry 5
and alcoholsrdquo Journal of Organic Chemistry vol 65 no 20 pp6368ndash6380 2000
[6] S T Handy J J Sabatini Y Zhang and I Vulfova ldquoProtectionof poorly nucleophilic pyrrolesrdquoTetrahedron Letters vol 45 no26 pp 5057ndash5060 2004
[7] P G M Wuts and T W Greene Greenersquos Protective Group inOrganic Synthesis JohnWily and Sons NewYork NY USA 4thedition 2007
[8] B Li R Bemish R A Buzon et al ldquoAqueous phosphoric acid asa mild reagent for deprotection of the t-butoxycarbonyl grouprdquoTetrahedron Letters vol 44 no 44 pp 8113ndash8115 2003
[9] D S Bose K K Kumar and A V N Reddy ldquoA new protocolfor selective deprotection of N-tert-butoxycarbonyl protectivegroup (t-Boc) with Sn(OTf)
2rdquo Synthetic Communications vol
33 no 3 pp 445ndash450 2003[10] N S Shaikh A S Gajare V H Deshpande and A V Bedekar
ldquoAmild procedure for the clay catalyzed selective removal of thetert- butoxycarbonyl protecting group from aromatic aminesrdquoTetrahedron Letters vol 41 no 3 pp 385ndash387 2000
[11] T Apelqvist and D Wensbo ldquoSelective removal of the N-Bocprotective group using silica gel at low pressurerdquo TetrahedronLetters vol 37 no 9 pp 1471ndash1472 1996
[12] V H Rawal R J Jones and M P Cava ldquoPhotocyclizationstrategy for the synthesis of antitumor agent CC-1065 synthesisof dideoxy PDE-I and PDE-II Synthesis of thiophene and furananalogues of dideoxy PDE-I and PDE-IIrdquo Journal of OrganicChemistry vol 52 no 1 pp 19ndash28 1987
[13] K Nadia B Malika K Nawel B MedYazid R Zine and N-EAouf ldquoSimple and efficient cleavage reaction of the Boc groupin heterocyclic compoundsrdquo Journal of Heterocyclic Chemistryvol 41 no 1 pp 57ndash60 2004
[14] I Hasan E R Marinelli L-C C Lin F W Fowler and AB Levy ldquoSynthesis and reactions of N-protected 2-lithiatedpyrroles and indoles The tert-butoxycarbonyl substituent as aprotecting grouprdquo Journal of Organic Chemistry vol 46 no 1pp 157ndash164 1981
[15] S El Kazzouli J Koubachi S Berteina-Raboin A Mouaddiband G Guillaumet ldquoAmild and selective method for the N-Bocdeprotection by sodium carbonaterdquo Tetrahedron Letters vol 47no 48 pp 8575ndash8577 2006
[16] N J Tom W M Simon H N Frost and M EwingldquoDeprotection of a primary Boc group under basic conditionsrdquoTetrahedron Letters vol 45 no 5 pp 905ndash906 2004
[17] S R Dandepally and A L Williams ldquoMicrowave-assistedN-Boc deprotection under mild basic conditions usingK3PO4sdotH2O in MeOHrdquo Tetrahedron Letters vol 50 no 9 pp
1071ndash1074 2009[18] GWang C Li J Li and X S Jia ldquoCatalyst-free water-mediated
N-Boc deprotectionrdquo Tetrahedron Letters vol 50 no 13 pp1438ndash1440 2009
[19] JWang Y-L Liang and J Qu ldquoBoiling water-catalyzed neutraland selective N-Boc deprotectionrdquo Chemical Communicationsno 34 pp 5144ndash5146 2009
[20] J S Yadav B V Subba Reddy K Premalatha and T SwamyldquoFirst example of the activation of polymethylhydrosiloxanewith molecular iodine a facile synthesis of 36-dihydropyranderivativesrdquo Tetrahedron Letters vol 46 no 15 pp 2687ndash26902005
[21] R Varala S Nuvula and S R Adapa ldquoMolecular iodine-cata-lyzed facile procedure for N-Boc protection of aminesrdquo Journalof Organic Chemistry vol 71 no 21 pp 8283ndash8286 2006
[22] Y-H Wang L Li and X-S Chen ldquoTheoretical studies on theiodine-catalyzed nucleophilic addition of acetone with five-membered heterocyclesrdquo Chemical Research in Chinese Univer-sities vol 24 no 4 pp 520ndash524 2008
[23] B P Bandgar and K A Shaikh ldquoMolecular iodine-catalyzedefficient and highly rapid synthesis of bis(indolyl)methanesunder mild conditionsrdquo Tetrahedron Letters vol 44 no 9 pp1959ndash1961 2003
[24] A C Legon ldquoPrereactive complexes of dihalogens XY withLewis bases B in the gas phase a systematic case for the halogenanalogue Bsdot sdot sdotXY of the hydrogen bond Bsdot sdot sdotHXrdquo AngewandteChemie vol 38 no 18 pp 2686ndash2714 1999
[25] G R Desiraju and R L Harlow ldquoCyano-halogen interactionsand their role in the crystal structures of the 4-halobenzoni-trilesrdquo Journal of the American Chemical Society vol 111 no 17pp 6757ndash6764 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
Journal of Chemistry 3
Table 2 Iodine-mediated deprotection of N-tert butylcarbamates (1) (Scheme 1)
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
1
NHBoc
1a 30
NH2
2a 98 94
2 1b
NHBoc
F50
NH2
2bF
90 82
3 1c
NHBoc
Cl90
NH2
2cCl
92 80
4 1d
NHBoc
Br120
NH2
2dBr
90 80
5 1e
NHBoc
CH3
90
NH2
2eCH3
82 80
6 1f
NHBoc
OH120
NH2
2fOH
90 85
7
NHBoc
1g
OH
H3C150
NH2
2g
OH
H3C86 80
4 Journal of Chemistry
Table 2 Continued
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
8
NHBoc
1hOCH3
60
NH2
2hOCH3
92 85
9
NHBoc
1iNO2
120
NH2
2iNO2
90 85
10
NHBoc
1j 90
NH2
2j 82 78
11
NBoc
1k 100
NH
2k 85 80
12
NBoc
1l
CHO
150
NH
2l
CHO
82 76
13
NBoc
1m
O
180
NH
2m
O
80 72
14
NBoc
1n
COOEt
240
NH
2n
COOEt
86 80
15
NBoc1o
O
120
NH2o
O
84 78aAll the reactions were carried out using the N-tert butylcarbamate 1 (10mmol) and iodine (008mmol) at room temperature
bIsolated yieldcAll the reactions were carried out using DCM (5mL) at room temperature for 5-6 h
References[1] G Sartori R Ballini F Bigi G Bosica R Maggi and P Righi
ldquoProtection (and deprotection) of functional groups in organicsynthesis by heterogeneous catalysisrdquo Chemical Reviews vol104 no 1 pp 199ndash250 2004
[2] E Gross and JMeienhoferThePeptides vol 3 Academic PressNew York NY USA 1981
[3] P J Kocienski Protecting Groups vol 185 chapter 6 Thieme-Stuttgart 1994
[4] G Theodoridis ldquoNitrogen protecting groups recent develop-ments and new applicationsrdquo Tetrahedron vol 56 no 16 pp2339ndash2358 2000
[5] Y Basel andAHassner ldquoDi-tert-butyl dicarbonate and 4-(dim-ethylamino)pyridine revisited Their reactions with amines
Journal of Chemistry 5
and alcoholsrdquo Journal of Organic Chemistry vol 65 no 20 pp6368ndash6380 2000
[6] S T Handy J J Sabatini Y Zhang and I Vulfova ldquoProtectionof poorly nucleophilic pyrrolesrdquoTetrahedron Letters vol 45 no26 pp 5057ndash5060 2004
[7] P G M Wuts and T W Greene Greenersquos Protective Group inOrganic Synthesis JohnWily and Sons NewYork NY USA 4thedition 2007
[8] B Li R Bemish R A Buzon et al ldquoAqueous phosphoric acid asa mild reagent for deprotection of the t-butoxycarbonyl grouprdquoTetrahedron Letters vol 44 no 44 pp 8113ndash8115 2003
[9] D S Bose K K Kumar and A V N Reddy ldquoA new protocolfor selective deprotection of N-tert-butoxycarbonyl protectivegroup (t-Boc) with Sn(OTf)
2rdquo Synthetic Communications vol
33 no 3 pp 445ndash450 2003[10] N S Shaikh A S Gajare V H Deshpande and A V Bedekar
ldquoAmild procedure for the clay catalyzed selective removal of thetert- butoxycarbonyl protecting group from aromatic aminesrdquoTetrahedron Letters vol 41 no 3 pp 385ndash387 2000
[11] T Apelqvist and D Wensbo ldquoSelective removal of the N-Bocprotective group using silica gel at low pressurerdquo TetrahedronLetters vol 37 no 9 pp 1471ndash1472 1996
[12] V H Rawal R J Jones and M P Cava ldquoPhotocyclizationstrategy for the synthesis of antitumor agent CC-1065 synthesisof dideoxy PDE-I and PDE-II Synthesis of thiophene and furananalogues of dideoxy PDE-I and PDE-IIrdquo Journal of OrganicChemistry vol 52 no 1 pp 19ndash28 1987
[13] K Nadia B Malika K Nawel B MedYazid R Zine and N-EAouf ldquoSimple and efficient cleavage reaction of the Boc groupin heterocyclic compoundsrdquo Journal of Heterocyclic Chemistryvol 41 no 1 pp 57ndash60 2004
[14] I Hasan E R Marinelli L-C C Lin F W Fowler and AB Levy ldquoSynthesis and reactions of N-protected 2-lithiatedpyrroles and indoles The tert-butoxycarbonyl substituent as aprotecting grouprdquo Journal of Organic Chemistry vol 46 no 1pp 157ndash164 1981
[15] S El Kazzouli J Koubachi S Berteina-Raboin A Mouaddiband G Guillaumet ldquoAmild and selective method for the N-Bocdeprotection by sodium carbonaterdquo Tetrahedron Letters vol 47no 48 pp 8575ndash8577 2006
[16] N J Tom W M Simon H N Frost and M EwingldquoDeprotection of a primary Boc group under basic conditionsrdquoTetrahedron Letters vol 45 no 5 pp 905ndash906 2004
[17] S R Dandepally and A L Williams ldquoMicrowave-assistedN-Boc deprotection under mild basic conditions usingK3PO4sdotH2O in MeOHrdquo Tetrahedron Letters vol 50 no 9 pp
1071ndash1074 2009[18] GWang C Li J Li and X S Jia ldquoCatalyst-free water-mediated
N-Boc deprotectionrdquo Tetrahedron Letters vol 50 no 13 pp1438ndash1440 2009
[19] JWang Y-L Liang and J Qu ldquoBoiling water-catalyzed neutraland selective N-Boc deprotectionrdquo Chemical Communicationsno 34 pp 5144ndash5146 2009
[20] J S Yadav B V Subba Reddy K Premalatha and T SwamyldquoFirst example of the activation of polymethylhydrosiloxanewith molecular iodine a facile synthesis of 36-dihydropyranderivativesrdquo Tetrahedron Letters vol 46 no 15 pp 2687ndash26902005
[21] R Varala S Nuvula and S R Adapa ldquoMolecular iodine-cata-lyzed facile procedure for N-Boc protection of aminesrdquo Journalof Organic Chemistry vol 71 no 21 pp 8283ndash8286 2006
[22] Y-H Wang L Li and X-S Chen ldquoTheoretical studies on theiodine-catalyzed nucleophilic addition of acetone with five-membered heterocyclesrdquo Chemical Research in Chinese Univer-sities vol 24 no 4 pp 520ndash524 2008
[23] B P Bandgar and K A Shaikh ldquoMolecular iodine-catalyzedefficient and highly rapid synthesis of bis(indolyl)methanesunder mild conditionsrdquo Tetrahedron Letters vol 44 no 9 pp1959ndash1961 2003
[24] A C Legon ldquoPrereactive complexes of dihalogens XY withLewis bases B in the gas phase a systematic case for the halogenanalogue Bsdot sdot sdotXY of the hydrogen bond Bsdot sdot sdotHXrdquo AngewandteChemie vol 38 no 18 pp 2686ndash2714 1999
[25] G R Desiraju and R L Harlow ldquoCyano-halogen interactionsand their role in the crystal structures of the 4-halobenzoni-trilesrdquo Journal of the American Chemical Society vol 111 no 17pp 6757ndash6764 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
4 Journal of Chemistry
Table 2 Continued
Entry N-tert butylcarbamates (1) Time (min) Producta (2) Yieldb () Yieldc () DCM solvent
8
NHBoc
1hOCH3
60
NH2
2hOCH3
92 85
9
NHBoc
1iNO2
120
NH2
2iNO2
90 85
10
NHBoc
1j 90
NH2
2j 82 78
11
NBoc
1k 100
NH
2k 85 80
12
NBoc
1l
CHO
150
NH
2l
CHO
82 76
13
NBoc
1m
O
180
NH
2m
O
80 72
14
NBoc
1n
COOEt
240
NH
2n
COOEt
86 80
15
NBoc1o
O
120
NH2o
O
84 78aAll the reactions were carried out using the N-tert butylcarbamate 1 (10mmol) and iodine (008mmol) at room temperature
bIsolated yieldcAll the reactions were carried out using DCM (5mL) at room temperature for 5-6 h
References[1] G Sartori R Ballini F Bigi G Bosica R Maggi and P Righi
ldquoProtection (and deprotection) of functional groups in organicsynthesis by heterogeneous catalysisrdquo Chemical Reviews vol104 no 1 pp 199ndash250 2004
[2] E Gross and JMeienhoferThePeptides vol 3 Academic PressNew York NY USA 1981
[3] P J Kocienski Protecting Groups vol 185 chapter 6 Thieme-Stuttgart 1994
[4] G Theodoridis ldquoNitrogen protecting groups recent develop-ments and new applicationsrdquo Tetrahedron vol 56 no 16 pp2339ndash2358 2000
[5] Y Basel andAHassner ldquoDi-tert-butyl dicarbonate and 4-(dim-ethylamino)pyridine revisited Their reactions with amines
Journal of Chemistry 5
and alcoholsrdquo Journal of Organic Chemistry vol 65 no 20 pp6368ndash6380 2000
[6] S T Handy J J Sabatini Y Zhang and I Vulfova ldquoProtectionof poorly nucleophilic pyrrolesrdquoTetrahedron Letters vol 45 no26 pp 5057ndash5060 2004
[7] P G M Wuts and T W Greene Greenersquos Protective Group inOrganic Synthesis JohnWily and Sons NewYork NY USA 4thedition 2007
[8] B Li R Bemish R A Buzon et al ldquoAqueous phosphoric acid asa mild reagent for deprotection of the t-butoxycarbonyl grouprdquoTetrahedron Letters vol 44 no 44 pp 8113ndash8115 2003
[9] D S Bose K K Kumar and A V N Reddy ldquoA new protocolfor selective deprotection of N-tert-butoxycarbonyl protectivegroup (t-Boc) with Sn(OTf)
2rdquo Synthetic Communications vol
33 no 3 pp 445ndash450 2003[10] N S Shaikh A S Gajare V H Deshpande and A V Bedekar
ldquoAmild procedure for the clay catalyzed selective removal of thetert- butoxycarbonyl protecting group from aromatic aminesrdquoTetrahedron Letters vol 41 no 3 pp 385ndash387 2000
[11] T Apelqvist and D Wensbo ldquoSelective removal of the N-Bocprotective group using silica gel at low pressurerdquo TetrahedronLetters vol 37 no 9 pp 1471ndash1472 1996
[12] V H Rawal R J Jones and M P Cava ldquoPhotocyclizationstrategy for the synthesis of antitumor agent CC-1065 synthesisof dideoxy PDE-I and PDE-II Synthesis of thiophene and furananalogues of dideoxy PDE-I and PDE-IIrdquo Journal of OrganicChemistry vol 52 no 1 pp 19ndash28 1987
[13] K Nadia B Malika K Nawel B MedYazid R Zine and N-EAouf ldquoSimple and efficient cleavage reaction of the Boc groupin heterocyclic compoundsrdquo Journal of Heterocyclic Chemistryvol 41 no 1 pp 57ndash60 2004
[14] I Hasan E R Marinelli L-C C Lin F W Fowler and AB Levy ldquoSynthesis and reactions of N-protected 2-lithiatedpyrroles and indoles The tert-butoxycarbonyl substituent as aprotecting grouprdquo Journal of Organic Chemistry vol 46 no 1pp 157ndash164 1981
[15] S El Kazzouli J Koubachi S Berteina-Raboin A Mouaddiband G Guillaumet ldquoAmild and selective method for the N-Bocdeprotection by sodium carbonaterdquo Tetrahedron Letters vol 47no 48 pp 8575ndash8577 2006
[16] N J Tom W M Simon H N Frost and M EwingldquoDeprotection of a primary Boc group under basic conditionsrdquoTetrahedron Letters vol 45 no 5 pp 905ndash906 2004
[17] S R Dandepally and A L Williams ldquoMicrowave-assistedN-Boc deprotection under mild basic conditions usingK3PO4sdotH2O in MeOHrdquo Tetrahedron Letters vol 50 no 9 pp
1071ndash1074 2009[18] GWang C Li J Li and X S Jia ldquoCatalyst-free water-mediated
N-Boc deprotectionrdquo Tetrahedron Letters vol 50 no 13 pp1438ndash1440 2009
[19] JWang Y-L Liang and J Qu ldquoBoiling water-catalyzed neutraland selective N-Boc deprotectionrdquo Chemical Communicationsno 34 pp 5144ndash5146 2009
[20] J S Yadav B V Subba Reddy K Premalatha and T SwamyldquoFirst example of the activation of polymethylhydrosiloxanewith molecular iodine a facile synthesis of 36-dihydropyranderivativesrdquo Tetrahedron Letters vol 46 no 15 pp 2687ndash26902005
[21] R Varala S Nuvula and S R Adapa ldquoMolecular iodine-cata-lyzed facile procedure for N-Boc protection of aminesrdquo Journalof Organic Chemistry vol 71 no 21 pp 8283ndash8286 2006
[22] Y-H Wang L Li and X-S Chen ldquoTheoretical studies on theiodine-catalyzed nucleophilic addition of acetone with five-membered heterocyclesrdquo Chemical Research in Chinese Univer-sities vol 24 no 4 pp 520ndash524 2008
[23] B P Bandgar and K A Shaikh ldquoMolecular iodine-catalyzedefficient and highly rapid synthesis of bis(indolyl)methanesunder mild conditionsrdquo Tetrahedron Letters vol 44 no 9 pp1959ndash1961 2003
[24] A C Legon ldquoPrereactive complexes of dihalogens XY withLewis bases B in the gas phase a systematic case for the halogenanalogue Bsdot sdot sdotXY of the hydrogen bond Bsdot sdot sdotHXrdquo AngewandteChemie vol 38 no 18 pp 2686ndash2714 1999
[25] G R Desiraju and R L Harlow ldquoCyano-halogen interactionsand their role in the crystal structures of the 4-halobenzoni-trilesrdquo Journal of the American Chemical Society vol 111 no 17pp 6757ndash6764 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
Journal of Chemistry 5
and alcoholsrdquo Journal of Organic Chemistry vol 65 no 20 pp6368ndash6380 2000
[6] S T Handy J J Sabatini Y Zhang and I Vulfova ldquoProtectionof poorly nucleophilic pyrrolesrdquoTetrahedron Letters vol 45 no26 pp 5057ndash5060 2004
[7] P G M Wuts and T W Greene Greenersquos Protective Group inOrganic Synthesis JohnWily and Sons NewYork NY USA 4thedition 2007
[8] B Li R Bemish R A Buzon et al ldquoAqueous phosphoric acid asa mild reagent for deprotection of the t-butoxycarbonyl grouprdquoTetrahedron Letters vol 44 no 44 pp 8113ndash8115 2003
[9] D S Bose K K Kumar and A V N Reddy ldquoA new protocolfor selective deprotection of N-tert-butoxycarbonyl protectivegroup (t-Boc) with Sn(OTf)
2rdquo Synthetic Communications vol
33 no 3 pp 445ndash450 2003[10] N S Shaikh A S Gajare V H Deshpande and A V Bedekar
ldquoAmild procedure for the clay catalyzed selective removal of thetert- butoxycarbonyl protecting group from aromatic aminesrdquoTetrahedron Letters vol 41 no 3 pp 385ndash387 2000
[11] T Apelqvist and D Wensbo ldquoSelective removal of the N-Bocprotective group using silica gel at low pressurerdquo TetrahedronLetters vol 37 no 9 pp 1471ndash1472 1996
[12] V H Rawal R J Jones and M P Cava ldquoPhotocyclizationstrategy for the synthesis of antitumor agent CC-1065 synthesisof dideoxy PDE-I and PDE-II Synthesis of thiophene and furananalogues of dideoxy PDE-I and PDE-IIrdquo Journal of OrganicChemistry vol 52 no 1 pp 19ndash28 1987
[13] K Nadia B Malika K Nawel B MedYazid R Zine and N-EAouf ldquoSimple and efficient cleavage reaction of the Boc groupin heterocyclic compoundsrdquo Journal of Heterocyclic Chemistryvol 41 no 1 pp 57ndash60 2004
[14] I Hasan E R Marinelli L-C C Lin F W Fowler and AB Levy ldquoSynthesis and reactions of N-protected 2-lithiatedpyrroles and indoles The tert-butoxycarbonyl substituent as aprotecting grouprdquo Journal of Organic Chemistry vol 46 no 1pp 157ndash164 1981
[15] S El Kazzouli J Koubachi S Berteina-Raboin A Mouaddiband G Guillaumet ldquoAmild and selective method for the N-Bocdeprotection by sodium carbonaterdquo Tetrahedron Letters vol 47no 48 pp 8575ndash8577 2006
[16] N J Tom W M Simon H N Frost and M EwingldquoDeprotection of a primary Boc group under basic conditionsrdquoTetrahedron Letters vol 45 no 5 pp 905ndash906 2004
[17] S R Dandepally and A L Williams ldquoMicrowave-assistedN-Boc deprotection under mild basic conditions usingK3PO4sdotH2O in MeOHrdquo Tetrahedron Letters vol 50 no 9 pp
1071ndash1074 2009[18] GWang C Li J Li and X S Jia ldquoCatalyst-free water-mediated
N-Boc deprotectionrdquo Tetrahedron Letters vol 50 no 13 pp1438ndash1440 2009
[19] JWang Y-L Liang and J Qu ldquoBoiling water-catalyzed neutraland selective N-Boc deprotectionrdquo Chemical Communicationsno 34 pp 5144ndash5146 2009
[20] J S Yadav B V Subba Reddy K Premalatha and T SwamyldquoFirst example of the activation of polymethylhydrosiloxanewith molecular iodine a facile synthesis of 36-dihydropyranderivativesrdquo Tetrahedron Letters vol 46 no 15 pp 2687ndash26902005
[21] R Varala S Nuvula and S R Adapa ldquoMolecular iodine-cata-lyzed facile procedure for N-Boc protection of aminesrdquo Journalof Organic Chemistry vol 71 no 21 pp 8283ndash8286 2006
[22] Y-H Wang L Li and X-S Chen ldquoTheoretical studies on theiodine-catalyzed nucleophilic addition of acetone with five-membered heterocyclesrdquo Chemical Research in Chinese Univer-sities vol 24 no 4 pp 520ndash524 2008
[23] B P Bandgar and K A Shaikh ldquoMolecular iodine-catalyzedefficient and highly rapid synthesis of bis(indolyl)methanesunder mild conditionsrdquo Tetrahedron Letters vol 44 no 9 pp1959ndash1961 2003
[24] A C Legon ldquoPrereactive complexes of dihalogens XY withLewis bases B in the gas phase a systematic case for the halogenanalogue Bsdot sdot sdotXY of the hydrogen bond Bsdot sdot sdotHXrdquo AngewandteChemie vol 38 no 18 pp 2686ndash2714 1999
[25] G R Desiraju and R L Harlow ldquoCyano-halogen interactionsand their role in the crystal structures of the 4-halobenzoni-trilesrdquo Journal of the American Chemical Society vol 111 no 17pp 6757ndash6764 1989
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Inorganic ChemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Carbohydrate Chemistry
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
Physical Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2014
Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
SpectroscopyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Medicinal ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chromatography Research International
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Applied ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Theoretical ChemistryJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Spectroscopy
Analytical ChemistryInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Quantum Chemistry
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Organic Chemistry International
ElectrochemistryInternational Journal of
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
CatalystsJournal of