Chapter 1 3

Nitrogen, Sulfur, and Phosphorus Compounds

I. Nitrogen Compounds 388 II. Sulfur Compounds 392

III. Phosphorus Compounds 395 References 395 Additional Reading 397

The autoxidations of nitrogen, sulfur, and phosphorus compounds tend to be complex, nonselective processes.1 Indeed, sulfur2- and phosphorus3-containing compounds react so readily with alkylperoxy radicals that they are often used as inhibitors of autoxidations. In this chapter we shall be concerned primarily with the selective oxidations of these substrates by H 2 0 2 and R 0 2 H in the presence of metal catalysts. These substrates react with peroxides via nucleophilic attack on the O—O bond. For example, the oxidation of tertiary amines to the corresponding amine oxides with organic peracids is a well-known reaction.4

o

R 3 N ^ O ^ O C R ' ► [R3NOH+ 0 2 C R ] ► R3NO + R C 0 2 H ( l ) H >►

Similar oxidations with the less electrophilic R 0 2 H and H 2 0 2 are much slower. Oxidation with these reagents becomes facile, however, in the pres-ence of high-valent transition metal catalysts such as Mo(VI), W(VI), V(V), and Ti(IV) and other Lewis acid catalysts such as Se(IV) and B(III), which promote heterolysis of peroxides.5,6 The mechanisms of these reactions, which involve inorganic peracids or related compounds as putative inter-mediates, have been discussed in Chapter 3.

387

388 13. Nitrogen, Sulfur, and Phosphorus Compounds

I. NITROGEN COMPOUNDS

Primary amines possessing an a-C—H bond are oxidized to oximes in 60-80% yield with hydrogen peroxide in the presence of the sodium salts of tungstic, molybdic, or vanadic acid.7-9

R R

> H N H ^ [Mocv-^cW > = N O H (2) R L R

This general reaction is of particular interest when applied to the conversion of cyclohexylamine to cyclohexanone oxime, an intermediate for nylon 6. More recent work10,11 has shown that cyclohexylamine is selectively oxi-dized to cyclohexanone oxime with alkyl hydroperoxides in the presence of Mo, W, V, and Ti catalysts in hydrocarbon solvents at 80°-100°C. The reaction proceeds via the hydroxylamine, which becomes the major product at room temperature.10

NH, NHOH NOH

+R°^H ^w Γ j ^^ Γ j + R O H + R 2 ° (3)

Titanium catalysts, such as («-BuO)4Ti, give the best results (selectivity >90%). 1 ( U 1

The catalytic oxidation of primary amines to imines by dioxygen in the presence of RuCl3 has been reported.12 For example, 2-aminohexane gave the corresponding imine (39%) together with 2-hexanone (31%), the product of imine hydrolysis.

[RuCl3] . - ^ν . . H 2 0

Benzylamine and fl-buty lamine afforded the corresponding nitriles, pre-sumably via further oxidation of the intermediate imine.

RCH2NH2 i ^ l · ^ RCH=NH ^ ^ % R C ^ N ( 5 )

By analogy with the oxidation of alcohols by Group VIII metal complexes (see Chapters 7 and 12), these reactions probably involve a ß-hydride elimi-nation mechanism :

H

X C Í Mn+ ► XC=N—H + HMn+ (6) y r I ^ I

H X X

/. Nitrogen Compounds 389

Similar oxidations can also be affected with oxometal reagents.13 For example, in the RuCl3 catalyzed oxidation of benzylamine to benzonitrile with peroxydisulfate,13a the active oxidant is the ruthenate anion Ru0 4

2 ~ . Potassium ferrate (K2Fe04) prepared by sodium hypochlorite oxidation of ferric nitrate, on the other hand, oxidizes primary amines to the corre-sponding aldehydes.13b These reactions presumably involve the initial for-mation of an imine intermediate via a cyclic transition state, followed by hydrolysis to the aldehyde in the case of F e 0 4

2 " , or by further oxidation to the nitrile in the case of R u 0 4

2 ".

H M = O

R - C f ^ — ^9KX R C H =NH - < ¿ V¿ N ► RCHO

Primary amines are also oxidized to the corresponding nitriles with sodium hypochlorite under phase transfer condions with tetraalkylammonium salts in the absence of transition metals as catalyst.130

Reaction of primary amines with stoichiometric amounts of PdCl2 in the presence of carbon monoxide results in the formation of isocyanates via oxidative carbonylation.14

RNH2 + CO + PdCl2 ► RNCO + Pd° + 2 HC1 (7)

Catalytic oxidation is observed with the system Pd(II)/Cu(II)/02, resulting in the formation of ureas, presumably via an intermediate isocyanate,15

RNH2 + CO [Pd^U"]> RNHCONHR (8)

where R = Me, Bu, PhCH2. Primary aliphatic amines in which the NH 2 group is attached to a tertiary

carbon atom are oxidized to the corresponding nitro compounds with H 2 0 2

in the presence of sodium tungstate, presumably via the nitrosoalkane as intermediate.7,9

I [Na2W04] I — C—NH2 + 3 H 2 0 2

J — i — ^ — G - N 0 2 + 4 H 2 0 (9)

The products of oxidation of aniline with TBHP depend on the particular metal catalyst used. In the presence of molybdenum or vanadium catalysts, the corresponding nitrobenzenes are formed.16

ArNH2 + 3 /-Bu02H [ M° , V ]> ArN0 2 + 3 /-BuOH + H 2 0 (10)

In the presence of titanium(IV) catalysts, on the other hand, the corre-sponding azoxy compounds are formed.17

390 13. Nitrogen, Sulfur, and Phosphorus Compounds

O

2 ArNH2 + 3 i-Bu02H -—±> A r N = N A r + 3 i-BuOH + 2 H 2 0 (11)

Secondary amines are oxidized by H 2 0 2 /Na 2 W04 to the corresponding hydroxylamines.7'9

R R ^ N H + H 2 0 2

[Na2W°-]) ^ N O H + H 2 0 (12) R R

The latter are, however, rather unstable and undergo further oxidation and/or condensation reactions. The corresponding reactions with alkyl hy-droperoxides, which would be expected to be more selective, do not appear to have been studied.

The oxidation of cyclic secondary amines with TBHP in the presence of manganese(II) catalysts affords the corresponding imides in 65-85% yield via lactam intermediates.18

O II

^CH? ^ C H T C TBHP ,_ ^ \ TBHP

(CH2)„ NH - p ^ (CH2)„ NH ^ ¡ ^ (CH2)„ NH (13)

CH2 C C II II

o o

In contrast to the reactions described above, reaction 13 almost certainly involves a homolytic mechanism (see Chapter 3).

A conversion of a secondary amine to an amide similar to that in eq 13 can be affected by sodium periodate in the presence of catalytic amounts o f R u 0 4 ,

I \ [RuQj , J \ \ ^ > - C 0 2 M e K^aqNalO^ 0 = ^ ^ C O . M e

COR COR

in a two-phase system consisting of carbon tetrachloride or chloroform and water.183 [When R = CH3, C2H5, cyclo-C6Hn and PhCH2, the yields of amide are 91, 80, 92 and 54%, respectively.] This transformation constitutes a key step in the chiral synthesis of L-glutamic acid from L-proline.

Secondary amines undergo oxidative carbonylation with CO/0 2 mixtures in the presence of copper salts as catalysts in methanol solvent at ambient temperature.19

2 R 2 N H + CO + ¿ 0 2 [Cu'/Cu"]> R2NCONR2 + H 2 0 (14)

/, Nitrogen Compounds 391

The cyclic secondary amines piperidine and morpholine react particularly smoothly. The reaction was suggested to involve the following steps.

R2NH + Cu" > R2N- + CuI + H+ (15)

R.N' + fCO^Cu1 > R2N—C- + Cu!(CO) (16)

O

R 2 N—O + Cu11 ► R 2 N = C = 0 + CuI (17)

O

R 2 N = C = 0 + R2NH ► R2NCONR2 + H + (18)

Tertiary amines are readily oxidized to the corresponding amine oxides with TBHP in the presence of molybdenum and vanadium catalysts.20"22

Vanadium compounds are the catalysts of choice.20

[VO(acac)2] / i r v . R3N + /-Bu02H -* R3NO + i-BuOH (19)

Tolstikov and co-workers23"25 used TAHP in the presence of molyb-denum catalysts for the oxidation of a wide variety of nitrogen heterocycles to the corresponding TV-oxides. Reaction rates and selectivities were signifi-cantly higher than those observed in the corresponding reactions with peracids. For example, acridine was oxidized quantitatively to its TV-oxide in 2 hrs with TAHP/MoCl5, whereas perbenzoic acid gives 50% conversion after several days.

OOD Ä O D D <*» Interestingly, bipyridyl, phenanthroline, and 8-hydroxyquinoline were not oxidized, presumably because they bind too strongly to the catalyst, thus hindering complex formation with the hydroperoxide (see Chapter 3).

¡mines (Schiff bases) are readily oxidized by TAHP to the corresponding oxaziridines, in 80-95% yield, with catalytic amounts of Mo(CO)6 or MoCl5.23'24

R \ TAHP R \ / \ , - . .

/ C = N - R - IMSTT > - * - * " (21) R R

Oxaziridines containing aromatic and aliphatic constituents were formed smoothly, but attempts to prepare purely aromatic oxaziridines were un-successful. Thus, the oxidation of benzylidene aniline was accompanied by vigorous rearrangement of the intermediate oxaziridine to benzanilide.

392 13. Nitrogen, Sulfur, and Phosphorus Compounds

Nitrosamines are oxidized to the corresponding nitramines with TAHP in the presence of molybdenum catalysts.23

;N—NO R'

[Movl] ;N—NO, (22)

R'

Nitroalkanes are converted to carbonyl compounds by reaction of the nitronate salt with TBHP in the presence of VO(acac)2 as catalyst.26

X H N O , f-BuOK

R' , , / C = N :

o

o

TBHP

[VO(acac)2]

R OH C

/ \ R' N 0 2

- H N 0 2

;c=o

(23)

This method provides a synthetically useful alternative to the Nef reaction,27

which requires strongly acidic conditions. It was used as a key step in the synthesis of a prostaglandin synthon.26

CH(OEt)2

J-BuOK

TBHP,[VO(acac)2]

ChN

CH(OEt)2

(24)

II. SULFUR COMPOUNDS

Sulfides are oxidized to the corresponding sulfoxides with hydrogen per-oxide28 or alkyl hydroperoxides29"34 in the presence of Mo, W, Ti and V catalysts. In the presence of excess hydroperoxide, further oxidation to the sulfone occurs.

R,S RO2H

[Mo v \ Vv] » R,SO

RQ2H

[MoVI, V v ] > R 2 S0 2 (25)

Sulfides are generally oxidized much faster than olefins. For example, with TBHP/VO(acac)2 in ethanol at 25°C, the relative rates decreased in the order ^-Bu2S (100) > ^-BuSPh (58) > «-Bu2SO (1.7) > cyclohexene (0.2).31

Unsaturated sulfides are selectively oxidized at the sulfur atom (see Chapter 3 for an example).30

The high rates of oxidation and virtually quantitative yields obtained under mild conditions emphasize the synthetic utility of the hydroperoxide-metal catalyst reagents for the conversion of sulfides to sulfoxides and sulfones. Tolstikov and co-workers,33,34 for example, used TAHP/MoCl5

//. Sulfur Compounds 393

for the oxidation of a wide variety of sulfides to sulfoxides and sulfones, many of which could not be selectively oxidized with organic peracids or other reagents.

When the oxidation of unsymmetric sulfides was carried out with TBHP/ VO(acac)2 in a mixture of benzene and a chiral alcohol, such as ( —)-menthol, as solvent, asymmetric induction was observed, although enantiomeric ex-cesses were rather low (5-10%).35

The use of H 2 0 2 in the presence of Se0 23 6 or ArSe02H3 7 for the facile,

selective oxidation of sulfides to sulfoxides has also been reported. The active oxidizing agents are presumably the perseleninic acids :

R S e ^ + H 2 0 2 ► RSe + H 2 0 (26) OH OOH

where R = Ar or HO

R S e ^ + R 2 S ► R S e ^ + R'2SO (27) OOH OH

Sulfides also undergo oxidation with peroxide-metal catalyst reagents via homolytic pathways. For example, the reaction of tert-butyl peracetate with dialkyl sulfides in the presence of copper ions affords a-acetoxy deriva-tives without oxidation of the sulfur atom.38"40 This is an example of the peroxy ester reaction (see Chapter 3).

¿-BuO.Ac + Cu1 ► Cu"OAc + /-BuO· (28)

¿-BuO- + RCH2SR' ^ RCHSR' + i-BuOH (29)

RCHSR' + Cu"OAc ► RCHSR' + Cu1 (30)

OAc

Thiols are readily oxidized to disulfides by dioxygen in basic media.41

The reaction involves the intermediary of thiyl (RS ·) radicals formed by one-electron oxidation of the thiolate anion (compare carbanion autoxidations).

R S + O 2 ► RS- + O2T (31)

2RS · ► RSSR (32)

The autoxidation of thiols is catalyzed by typical one-electron oxidants, e.g., Cu(II), Fe(III), Mn(III), and Co(III).41 These catalysts are usually employed to enhance the rate of oxidation. A number of studies of the interactions of metal compounds with thiols have been carried out.4 2 - 4 6

For example, stoichiometric oxidation of thiols with ferric octanoate pro-ceeds via the following steps,43 involving inner-sphere oxidation of RS" by Fe(III).

394 13. Nitrogen, Sulfur, and Phosphorus Compounds

XFeHI + RSH ► RSFem + HX (33)

RSFe111 ► Fe" + RS· (34)

The intermediate thiyl radicals could be intercepted by the addition of olefins, resulting in the formation of sulfides via the following chain propa-gation sequence [i.e., the Fe(III) acts as an initiator].

RS· + R'CH=CH2 ► RSCH2CHR' (35)

RSCH2CHR' + RSH ► RSCH2CH2R + RS· (36)

In contrast, when Mn(III) acetylacetonate was the stoichiometric oxidant, interception of thiyl radicals by added olefin was inefficient.42 This was attributed to effective interception of the thiyl radicals by Mn(III) :

RS· + Mnm ► RS+ + Mn" (37)

RS+ + RSH ► RSSR + H + (38)

The cooxidation of thiols and olefins results in the formation of ß-sulfinyl alcohols via rearrangement of intermediate ß-thiohydroperoxides (see Chapter 2).47

R S H + ^ C = C ^ + 0 2 ► RS—C—C—02H ► RS—C—C—OH (39)

I I II I I o

Cooxidation of thiols and acetylenes produces hemithioacetals of a-dicar-bonyl compounds, e.g.,48

PhC^CH + RSH + 0 2 ► Ph—C—CH—SR (40)

O OH

The product is unstable and thermally decomposes to the a-dicarbonyl compound. This constitutes a method for the overall conversion of an acetylene to an a-dicarbonyl compound (see Chapter 9).

PhC—CH—SR ► PhCCHO + RSH (41) II I II O OH O

The oxidation of thiols with TBHP in the presence of catalysts that promote the heterolysis of peroxides, e.g., Mo(VI) and V(V), produces sul-fonic acids, presumably via the corresponding sulfenic (RSOH) and sulfinic (RS02H) acids as intermediates:49

ΓΜονι V v l RSH + 3i-Bu02H '—± RS03H + 3 i-BuOH (42)

Hydrogen sulfide is oxidized by hexammineruthenium(IH) to elemental sulfur in aqueous solution.50

/// . Phosphorus Compounds 395

2(NH3)6Ru3 + + H 2 S ► 2(NH3)6Ru2 + + 2 H + + S (43)

This oxidation coupled with the ready reoxidation of the ruthenium(H) species by dioxygen,51 represents a potential for the catalytic coproduction of hydrogen peroxide according to the overall stoichiometry:

H2s + o2 [Ru] > s + H2o2

The first step in eq 43 probably proceeds via a one-equivalent oxidation to the sulfhydryl radical HS% since alkyl mercaptors yield alkyl dissulfides under the same conditions.

III. PHOSPHORUS COMPOUNDS

Trivalent phosphorus compounds readily undergo autoxidation to give more stable pentavalent compounds.52,53 Indeed, the autoxidation of tri-alkylphosphines can be so facile that they may even be pyrophoric. Reac-tions of trivalent phosphorus compounds with intermediate alkylperoxy radicals generally involve displacement and/or addition at the phosphorus atom.54

y > R O + R3P0 (44a)

R0 2 - + R3P /

\ ► R O 2 P R 2 + R · (44b)

These reactions have little synthetic utility. Triarylphosphines and trialkyl or triaryl phosphites are more stable toward oxidation. Smooth oxidation of these compounds has been accomplished, however, using TBHP in the presence of molybdenum and vanadium catalysts.55,56

ΓΜονι Vv1 Ar3P + í-Bu02H - ^ Λ Ar3PO + ¿-BuOH (45)

(RO)3P 4- i-Bu02H [ M° ,VV]) (RO)3PO + i-BuOH (46)

REFERENCES

1. L. Horner, in "Autoxidation and Antioxidants" (W. O. Lundberg, ed.), p. 171. Wiley, New York, 1961.

2. P. Koelewijn and H. Berger, Reel. Trav. Chim. Pays-Bas 91, 1275 (1972); 93, 63 (1974). 3. K. J. Humphris and G. Scott, Pure Appl. Chem. 36, 163 (1973); J. Chem. Soc, Perkin II

p. 826(1973). 4. A. R. Katritzky and J. M. Lagowski, "Chemistry of the Heterocyclic N-Oxides." Academic

Press, New York, 1971. 5. G. A. Tolstikov, V. P. Yurev, and U. M. Dzhemilev, Russ. Chem. Rev. 44, 319 (1975).

396 13. Nitrogen, Sulfur, and Phosphorus Compounds

6. R. A. Sheldon, Aspects of Homogeneous Catalysis (R. Ugo, ed.), 4 3, (1981). 7. P. Burckard, J. P. Fleury, and F. Weiss, Bui. Soc Chim. France p. 2730 (1965). 8. K. Kahr, Angew. Chem. 72, 135 (1960). 9. O. L. Lebedev and S. N. Kazarnovskii, Zh. Obshch. Khim. 30, 1631 (1960).

10. J. L. Russell and J. Kollar, U.S. Patent 1,100,672 (1965) to Halcón International. 11. G. N. Koshel, M. I. Farberov, L. L. Zalygin, and G. A. Krushinskaya, J. Appl. Chem.

C/SS* 44, 885(1971). 12. R. Tang, S. E. Diamond, N. Neary, and F. Mares, J. Chem. Soc, Chem. Commun, p. 562

(1978). 13. (a) M. Schroder and W. P. Griffith, J. Chem. Soc Chem. Commun, p. 58 (1979).

(b) R. J. Audette, J. W. Quail and P. J. Smith, Tetrahedron Lett. p. 279 (1971). (c) G. A. Lee and H. H. Freedman, Tetrahedron Lett. p. 1641 (1976).

14. E. W. Stern and M. L. Spector, J. Org. Chem. 26, 3126 (1961). 15. Y. L. Sheludyakov, V. A. Golodov, and D. V. Sokolskii, Dokl. Akad. Nauk SSSR 249(3),

658 (1979). 16. G. R. Howe and R. R. Hiatt, J. Org. Chem. 35, 4007 (1970). 17. K. Kosswig, Justus Liebigs Ann. Chem. 749, 206 (1971). 18. A. R. Doumaux and D. J. Trecker, J. Org. Chem. 35, 2124 (1970). 18a. S. Yoshifuji, H. Matsumoto, K. Tanaka and Y. Nitta, Tetrahedron. Lett. 21, 2963 (1980). 19. W. Brackman, Discuss. Faraday Soc 46, 122 (1968); see also J. Tsuji and N. Iwamoto,

J. Chem. Soc Chem. Commun, p. 380 (1966). 20. M. N. Sheng and J. G. Zajacek, J. Org. Chem. 33, 588 (1968). 21. M. N. Sheng and J. G. Zajacek, Org. Syn. 50, 56 (1970). 22. L. Kühnen, Chem. Ber. 99, 3384 (1966). 23. G. A. Tolstikov, U. M. Jemilev, V. P. Jurjev, F. B. Gershanov, and S. F. Rafikov, Tetrahe-

dron Lett.?. 2807(1971). 24. G. A. Tolstikov, U. M. Dzhemilev, and V. P. Yurev, J. Org. Chem. USSR 8, 1200 (1971). 25. G. A. Tolstikov, U. M. Dzhemilev, V. P. Yurev, A. A. Pozdeeva, and F. G. Gerchikova,

J. Gen. Chem. USSR 43, 1350 (1973). 26. P. A. Bartlett, F. R. Green, and T. R. Webb, Tetrahedron Lett. p. 331 (1977). 27. W. E. Noland, Chem. Rev. 55, 137 (1955). 28. H. S. Schultz, H. B. Freyermuth, and S. R. Bue, / . Org. Chem. 28, 1140 (1963). 29. L. Kühnen, Angew. Chem. 78, 957 (1966). 30. V. F. List and L. Kühnen, Erdoel & Kohle, Erdgas, Petrochem 20, 192 (1967). 31. R. Curci, F. DiFuria, R. Testi, and G. Modena, / . Chem. Soc, Perkin II p. 752 (1974). 32. R.Curci, F. DiFuria, and G. Modena, J. Chem. Soc, Perkin II p. 576 (1977); S. Cenci,

F. DiFuria, G. Modena, R. Curci, and J. O. Edwards, ibid. p. 979 (1978). 33. G. A. Tolstikov, U. M. Dzhemilev, N. N. Novitskaya, V. P. Yurev, and R. G. Kantyukova,

J. Gen. Chem. USSR 41, 1896 (1971). 34. G. A. Tolstikov, U. M. Dzhemilev, N. N. Novitskaya, and V. P. Yurev, Bul. Acad. Sei.

USSR, Div. Chem. Sei. 21, 2675 (1972). 35. F. DiFuria, G. Modena, and R. Curci, Tetrahedron Lett. p. 4637 (1976). 36. J. Drabowicz and M. Mikolajczyk, Synthesis p. 758 (1978). 37. H. J. Reich, F. Chow, and S. L. Peake, Synthesis p. 299 (1978). 38. S. O. Lawesson, C. Berglund, and S. Gronwall, Acta Chem. Scand. 15, 249 (1961). 39. S. O. Lawesson and C. Berglund, Acta Chem. Scand. 15, 36 (1961); C. Berglund and S. O.

Lawesson, ibid. 16, 773 (1962). 40. G. Sosnovsky, J. Org. Chem. 26, 281 (1961); Tetrahedron 18, 15, 903 (1962). 41. G. Capozzi and G. Modena, in "The Chemistry of the Thiol Group" (S. Patai, ed.), Part 2,

p. 785. Wiley, New York, 1974.

References 397

42. T. Nakaya, H. Arabori, and M. Imoto, Bui. Chem. Soc. Japan 43, 1888 (1970). 43. T. J. Wallace, J. Org. Chem. 31, 3071 (1966). 44. C. F. Cullis and D. L. Trimm, Discuss. Faraday Soc. 46, 144 (1968). 45. C. J. Swan and D. L. Trimm, Adv. Chem. Series 76, 182 (1968). 46. J. D. Hopton, C. J. Swan, and D. L. Trimm, Adv. Chem. Series 75, 216 (1968). 47. M. S. Kharasch, W. Nudenberg, and G. J. Mantell, J. Org. Chem. 16, 524 (1951). 48. K. Griesbaum, A. A. Oswald, and B. E. Hudson, J. Am. Chem. Soc. 85, 1969 (1963). 49. M. N. Sheng and J. G. Zajacek, U.S. Patent 3,670,002 (1972) to Atlantic Richfield. 50. S. E. Diamond, B. S. Tovrog and F. Mares, / . Am. Chem. Soc. 102, 5908 (1980). 51. D. M. Stanbury, O. Haas and H. Taube, Inorg. Chem. 19, 518 (1980). 52. S. A. Buckler, J. Am. Chem. Soc. 84, 3093 (1962). 53. M. B. Floyd and C. B. Boozer, / . Am. Chem. Soc. 85, 984 (1963). 54. G. A. Razuvaev, V. A. Shushunov, V. A. Dodonov, and T. G. Brilkina, in "Organic

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ADDITIONAL READING

J. P. Schirmann and S. Y. Delavarenne, "Hydrogen Peroxide in Organic Chemistry." In-formations Chimie, Paris, 1979.

G. Sosnovsky and D. J. Rawlinson, in "Organic Peroxides" (D. Swern, ed.), Vol. 1, p. 585. Wiley (Interscience), New York, 1970.

G. Sosnovsky and D. J. Rawlinson, in "Organic Peroxides" (D. Swern, ed.), Vol. 2, p. 153. Wiley (Interscience), New York, 1971.

G. Sosnovsky, in "Organic Peroxides", (D. Swern, ed.), Vol. 2, p. 269. Wiley (Interscience), New York, 1971.