synthesis of acetylenes, allenes and cumulenes || sulphenylation and related reactions

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E:/Archive files/4188-Brandsma/Printer-Files/4188-Chapter-08.3d

8Sulphenylation and Related Reactions

8.1 METHODS FOR THE DIRECT INTRODUCTION OFSULPHUR, SELENIUM AND TELLURIUM

The most practical methods for compounds containing the system C�C–S (and

the Se- or Te analogues) consist of reacting a metallated acetylene with ele-

mental sulphur (Se or Te) or a sulphenyl derivative with a suitable leaving

group L. Sulphoxides may be prepared by analogous coupling reactions.

The various methods can be represented by the following scheme (Y ¼ S,

Se, Te) [1]:

The insertion of a sulphur atom into the �C–metal bond is analogous to

the well-known formation of alkali thiocyanate from alkali cyanide and

sulphur. The insertion reaction has been successfully applied to introduce sul-

phur (or Se and Te) into an aromatic or heteroaromatic ring system. The

reaction of metallated acetylenes with the elements S, Se and Te constitutes

a ready access to several derivatives with the C�C–Y systems. Although

derivatisation of the mesomeric anion RC�C�Y�$R�C¼C¼Y with an

175

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‘electrophilic’ reagent ‘Eþ’ in principle may give products from both

structures, the only isolated type of derivative is RC�C–YE. In the case of

selenium and tellurium, yields of the alkylation products are significantly

better than with sulphur. The reactions with sulphur and subsequent deri-

vatisations usually give appreciable amounts of high-boiling residues,

which might in part result from further reactions of the thioketenes

RC(E)¼C¼S.

The insertions proceed most easily in liquid ammonia. However, functiona-

lisations in this solvent are restricted to alkylation reactions. Reactions in tetra-

hydrofuran or diethyl ether are generally carried out with lithium alkynylides,

which react much more smoothly than sodium or potassium derivatives

because of a better solubility. A wide variety of derivatives with the structure

system C�C–Y are accessible via the lithium chalcogenates RC�C–YLi in

organic solvents [1,20].

Alkali acetylides react very easily with disulphides, R1SSR1, thiocyanates,

R1SC�N, and thiosulphonates, R1SSO2R1. The reactions can be carried out

in liquid ammonia as well as in organic solvents and generally give excellent

yields of the acetylenic sulphides [2,3], RC�CSR1. Although sulphenyl halides

seem suitable reagents for the introduction of alkylthio or arylthio groups, they

are seldom used for this reaction, because of their sensitivity and the chance of

further reaction with the products.

Di(1-alkynyl) sulphides are formed in excellent yields, if (freshly distilled)

sulphur dichloride is added to a solution or suspension of a lithium alkynylide

in diethyl ether [4]. In an analogous manner, di(1-alkynyl) sulphoxides are

formed from thionyl chloride and alkynyllithium [4], while sulphinyl chlorides

R1S(¼O)Cl may be used to prepare the sulphoxides RC�CS(¼O)R1.

Preliminary experiments [2] suggest that interaction between alkynyllithium

and sulphonyl chlorides R1SO2Cl can give both sulphones RC�CSO2R1 and

chloroalkynes, RC�CCl.

There are few examples of analogous reactions with metallated allenes or

disubstituted acetylenes. Like in the case of functionalisation with other elec-

trophiles mixtures of acetylenic and allenic derivatives can be expected. An

exception is the reaction of 1-lithio-1-methoxyallene with dimethyl disulphide,

which affords 1-methoxy-1-methylthioallene, H2C¼C¼C(OMe)SMe as the

only product [5]. Allenyllithiums, R2C¼C¼CHLi, have been converted into

allenic sulphides [6], R2C¼C¼CHSR1 or selenides [7], R2C¼C¼CHSePh,

using R1SSR1 and PhSeSePh, respectively, as reagents. Reaction of alkyl sul-

phinates, RS(¼O)O-alkyl with allenic Grignards gives the sulphoxides with

the structures [8] RS(¼O)C(Me)¼C¼CHMe. In the case of an asymmetric

sulphur atom, induction of chirality takes place stereospecifically in the alle-

nic system.

176 8. SULPHENYLATION AND RELATED REACTIONS

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8.2 EXPERIMENTAL SECTION

Notes

1. For the preparation of alkali amides in liquid ammonia and alkyllithium

reagents see Chapter 2.

2. Most of the reactions in organic solvents or liquid ammonia at temperatures

below its boiling point are carried out under inert gas.

8.2.1 Reaction of metallated acetylenes with sulphenylatingagents in liquid ammonia

Scale: 0.20 molar; Apparatus: Figure 1.1, 500 ml, the thermometer is omitted

A convenient and quick method to prepare acetylenic sulphides consists

of adding a disulphide, thiosulphonate or thiocyanate to a lithium or sodium

alkynylide in liquid ammonia. The reaction proceeds almost instantaneously,

except in the case of di-(t-butyl) disulphide (reaction with RC�CLi in an

organic solvent at higher temperatures, or the use of t-BuSC�N may be con-

sidered). Ethynyl sulphides, HC�CSR1, cannot be obtained using this method,

since they are immediately deprotonated by alkali acetylide MC�CH and then

a second R1S group is introduced with the formation of the bis-thioethers

[2,17], R1SC�CSR1. Sulphides with conjugated unsaturated systems, e.g.

4-(alkylthio)-1-buten-3-ynes, H2C¼CHC�CSR1, and 1-(alkylthio)-1,3-alka-

diynes, RC�CC�CSR1, readily undergo nucleophilic addition of thiolate

R1S–. Therefore, thiocyanates or thiosulphonates should be used for the

sulphenylation of alkali compounds from 1,3-enynes and 1,3-diynes and also

in those cases in which there is a chance of a subsequent reaction of the product

with thiolate.

8.2.1.1 Procedure (cf. [3])

A solution or suspension of 0.22 mol of the lithium or sodium alkynylide in

250 ml of liquid ammonia is prepared as described in Chapter 3, exp. 3.9.3.

The disulphide, thiosulphonate [9] or thiocyanate (0.20 mol, see exp. 8.2.2,

diluted with 50 ml of Et2O, is added dropwise over 10 min with efficient

stirring. In many cases a rather thick suspension is formed: an additional

volume of � 100 ml of liquid ammonia may then be introduced. The ammonia

may either be removed by placing the flask in a water bath at 40 �C (after

8.2 EXPERIMENTAL SECTION 177

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having replaced the equipment on the outer necks with outlets), or allowed to

evaporate (Figure 1.7). After addition of 200 ml of Et2O to the solid residue,

300 ml of ice water is added with vigorous stirring or swirling by hand. After

separation of the layers, the aqueous phase is extracted with Et2O, and the

organic solution dried over MgSO4. The solvent is removed under reduced

pressure and the remaining liquid distilled in vacuo. The following examples

give an impression of the scope:

1-(Methylthio)-1-pentyne, n-PrC�CSMe, bp 50 �C/12 Torr, yield �90%,

from n-PrC�CLi, and MeSC�N; 1-[2-(methylthio)ethynyl]-1-cyclohexene,

1-cyclohexenylC�CSMe, bp 120 �C/12 Torr, in �85%, yield from 1-cyclohex-

enyllithium and MeSSMe; 1-(methylthio)-1,3-pentadiyne, MeC�CC�CSMe,

bp 80 �C/12 Torr, in �80%, yield from MeC�CC�CLi and MeSSO2Me,

1-[(4-chlorobutyl)thio]-1-propyne, MeC�CS(CH2)4Cl, bp � 90 �C/1 Torr,

yield �80%, from MeC�CLi and 4-chlorobutyl thiocyanate, Cl(CH2)4SC�N.

8.2.2 C-Thiomethylation of acetylenic alcohols in liquid ammonia

Scale: 0.10 molar; Apparatus: Figure 1.1, 500 ml, no thermometer

8.2.2.1 Procedure

2-Propyn-1-ol (0.10 mol) or 3-butyn-1-ol, (0.10 mol) is added dropwise over

10 min to a vigorously stirred suspension of 0.25 mol of lithium amide in 500 ml

of liquid ammonia (see Chapter 4, exp. 4.5.10). Most of the suspended material

disappears. Methylthiocyanate (0.25 mol (see below) is then added dropwise

over 10 min. The ammonia is subsequently removed by placing the flask in a

water bath at 40 �C, stirring being continued as long as possible (the dropping

funnel and the thermometer are removed). To the remaining dark residue

200 ml of ice water is added, after which five to ten extractions with Et2O

are carried out. The organic solution is dried over MgSO4 and subsequently

concentrated in vacuo using a rotary evaporator. Distillation of the remain-

ing liquid through a 30-cm Vigreux column gives 3-(methylthio)-2-propyn-1-ol,

MeSC�CCH2OH, bp � 60 �C/0.2 Torr, in �70% yield (redistillation gives bp

95 �C/12 Torr) and 4-(methylthio)-3-butyn-1-ol, MeSC�CCH2CH2OH, bp

108 �C/15 Torr, in �80% yield.

Methyl thiocyanate is prepared by adding at � 60 �C 1 mol of dimethyl

sulphate to a mixture of 1 mol of potassium thiocyanate and a small amount

(50 ml) of water. After an additional period of 45 min heating at 90 �C, ice


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water, just enough for dissolution of the salt, is added. The upper layer is dried

and distilled under normal pressure. The yield is excellent, provided that for the

reaction a small amount of water is used.

8.2.3 Reaction of lithiated acetylenes with sulphenylatingagents in diethyl ether or tetrahydrofuran

Scale: 0.10 molar; Apparatus: Figure 1.1, 500 ml

8.2.3.1 Procedure (for Introduction see exp. 8.2.1)

The sulphenyl compound (0.10 mol) is added over a few minutes to a solution

or suspension of 0.11 mol of RC�CLi in Et2O or THF (see Chapter 3,

exps. 3.9.4 and 3.9.6). This solution is cooled to �75 �C in the cases of X ¼

CN and MeSO2, or to –40 �C when X ¼MeS. The cooling bath is removed and

the temperature allowed rising to 0 �C. In the case of a very thick suspension,

an additional amount of Et2O or THF should be added. Ice water (100 ml) is

added to the vigorously stirred reaction mixture, followed by extraction of the

aqueous layer with Et2O and drying the organic solvent over MgSO4. The

following compounds have been prepared in yields of at least 80%:

1-(Methylthio)-1-hexyne, n-BuC�CSMe, bp 65 �C/12 Torr, (MeSSMe-

method); 3,3-dimethoxy-1-(methylthio)-1-propyne, (MeO)2CHC�CSMe, bp 86 �C/

12 Torr, (MeSC�N-method) and 3-chloro-1-(methylthio)-1-propyne, MeSC�

CCH2Cl, bp 65 �C/15 Torr, (MeSSO2Me-method).

1-[(2-Chloroethyl)thio]-1-propyne,MeC�CSCH2CH2Cl, bp 78�C/15 Torr, is

obtained in an excellent yield from MeC�CLi in THF–hexane (–70 �C! rt)

and 2-chloroethyl thiocyanate, N�CSCH2CH2Cl.

8.2.4 4-Ethylthio-1-buten-3-yne, 4-methylseleno-1-buten-3-yneand 4-methyltelluro-1-buten-3-yne from in-situ generatedvinylethynylsodium, sulphur, selenium or telluriumand alkyl halides


[13.1.2004–10:01pm] [175–190] [Page No. 180]


Scale: 0.10 molar (dichlorobutene); Apparatus: Figure 1.1, 500 ml; for

the addition of the elements the dropping funnel is replaced with a powder

funnel.

AlkylSe and alkylTe groups can be introduced by reaction with diselenides

and ditellurides, RYYR, but the desired products can be prepared in a more

practical and economical way by successive addition of the elements and the

alkyl halide. The insertion of the elements proceeds most easily in liquid

ammonia, provided that grey Te powder and red Se powder is used. Black

Te powder, obtained by precipitation, is not reactive, possibly because of the

presence of an oxide coating, while the black modification of Se, ‘selenium

nigrum’, is also less reactive. In Et2O or THF, temperatures in the range

0–20 �C are necessary for a smooth reaction of the elements.

8.2.4.1 Procedure (cf. [18,19])

(E)-1,4-Dichloro-2-butene (0.10 mol, commercially available, Note 1) is added

dropwise over 15 min to a suspension of 0.30 mol of sodamide in 300 ml of

liquid ammoniawith cooling between –35 and –40 �C.After an additional 15min

the dropping funnel is replaced with a powder funnel and dry, powdered

sulphur (3.0 g), red selenium (7.0 g) or grey tellurium (12 g) is introduced in

small portions over 15 min, while maintaining the temperature between –35

and –40 �C. Small amounts of the elements in the powder funnel and the neck

are rinsed into the reaction mixture with Et2O (20–40 ml). After an additional

15–30 min, when the powder has dissolved completely (Note 2), the reaction

mixture is cooled to –55 �C. Methyl iodide (0.15 mol) or ethyl bromide (0.17

mol) is added over a few seconds by syringe. After an additional 10 min the

cooling bath is removed and the mixture is stirred for 1 h. The ammonia is then

allowed to evaporate (Figure 1.7). After addition of water to the remaining salt

mass, the product is isolated by extraction with Et2O, drying of the extracts

over MgSO4 and concentration of the organic solution in vacuo (Note 3).

Distillation of the remaining liquid at <0.5 Torr, using a single receiver,

cooled in a bath at <–20 �C (Figure 1.10), gives 4-(methylseleno)-1-buten-3-

yne, H2C¼CHC�CSeMe, in � 80% and 4-(methyltelluro)-1-buten-3-yne,

H2C¼CHC�CTeMe, (yellowish-brown liquid), in � 70% yield. Pure

4-(ethylthio)-1-buten-3-yne H2C¼CHC�CSEt, bp 47 �C/10 Torr, is obtained

in � 55% yield by careful redistillation of the contents of the receiver.

Notes

1. The reaction of the (Z)-isomer with NaNH2 proceeds less satisfactorily,

and gives a considerable amount of resinous product.


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2. A small amount of coarse Te powder may remain.

3. The tellurium compound is air-sensitive, and the work-up should therefore

be carried out under nitrogen.

8.2.5 1-(Ethylseleno)-1-propyne and 1-(ethyltelluro)-1-propynefrom in-situ generated propynylsodium, selenium ortellurium and ethyl bromide

Scale: 0.10 molar (dibromopropane); Apparatus: Figure 1.1, 500 ml

8.2.5.1 Procedure (cf. exp. 8.2.4)

Red selenium powder (7.0 g) or grey tellurium powder (12.0 g) is added to a

suspension of 0.10 mol of propynylsodium in 200 ml of liquid ammonia

(Chapter 3, Table 3.1 and exp. 3.9.21). The addition is carried out over 15

min through a powder funnel, which temporarily replaces the dropping funnel.

During this addition the temperature of the reaction mixture is maintained

between –35 and –40 �C. Small amounts of powder in the funnel or in the

neck are rinsed into the flask with a few millilitres of Et2O. After 15 to 30

min the Se or Te has disappeared (a small amount of coarse Te powder may

remain unconverted). Ethyl bromide (0.15 mol) is then added over 15 min

without external cooling. After an additional 1 h stirring is stopped and the

ammonia is allowed to evaporate (Figure 1.7). The remaining salt is dissolved

by addition of 100 ml of water, after which the mixture is extracted four times

with Et2O. After drying the organic solution over MgSO4, the solvent is

removed by evacuation and the remaining liquid distilled through a 30-cm

Vigreux column.

1-(Ethylseleno)-1-propyne, MeC�CSeEt, bp 44 �C/10 Torr, and 1-(ethyltel-

luro)-1-propyne, MeC�CTeEt, bp 66 �C/10 Torr, are obtained in good yields.

Sodium acetylide, NaC�CH, selenium and ethyl bromide give bis (ethylsele-

no)acetylene, EtSeC�CSeEt. This compound is formed by disproportionation

[10] of the initially formed HC�CSeEt under the influence of HC�CSeNa.

8.2.6 Reaction of alkynyllithium in tetrahydrofuran withsulphur or selenium and subsequent alkylation


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8.2.6.1 Procedure

Dry, powdered sulphur (3.2 g) or red selenium (8.0 g) is added over a

few minutes to a solution of 1-alkynyllithium, RC�CLi (0.10 mol in 70 ml

of THF and 63 ml of hexane, Chapter 3, exp. 3.9.4), cooled at –40 �C. The

cooling bath is removed and the temperature allowed rising to 15 �C. After an

additional period of 15–30 min (when the powder has dissolved) 0.30 mol

(large excess) of bromochloromethane is added over a few seconds. In the

case of the preparation of sulphides, the brown solution is allowed to stand

for 12–15 h at rt, the alkyneselenolates react faster so that a period of about 4 h

is sufficient. The reaction mixture is poured into 150 ml of ice water and, after

vigorous shaking, the layers are separated. The organic layer and three ethereal

extracts are dried over MgSO4 and subsequently concentrated under reduced

pressure. The remaining liquid is first distilled at low (<0.5 Torr) pressure

through a very short column and the distillate collected in a single receiver

cooled below –30 �C (Figure 1.10). Redistillation gives the following products:

1-(chloromethylthio)-1-butyne, EtC�CSCH2Cl, bp 65 �C/12 Torr; 1-(chloro-

methylthio)-1-propyne, MeC�CSCH2Cl, bp 58 �C/12 Torr; 1-(chloro-

methylthio)-3,3-dimethyl-1-butyne, t-BuC�CSCH2Cl, bp 70 �C/12 Torr;

2-[(chloromethyl)thio]ethynyl(trimethyl)silane, Me3SiC�CSCH2Cl, bp 78 �C/

12 Torr; 1-(chloromethylseleno)-1-butyne, EtC�CSeCH2Cl, bp 35 �C/0.01

Torr. Yields of the sulphides are between 55 and 60%, the selenium compound

is obtained in >70% yield.

Thioethers and selenoethers RC�CYalkyl can be prepared by a similar

procedure using a lesser excess of an alkyl bromide or alkyl iodide.

8.2.7 Reaction of alkynethiolates with acetyl bromideand ethyl chloroformate

Scale: 0.20 molar; Apparatus: Figure 1.1, 1 litre


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8.2.7.1 Procedure [11] (cf. [20])

A suspension or solution of 0.20 mol of alkynyllithium in 140 ml of Et2O and

127 ml of hexane (Chapter 3, exp. 3.9.4) is cooled to –40 �C and 6.4 g dry,

powdered sulphur is added over 1 min. The cooling bath is removed and the

temperature allowed rising to rt. In all cases brown solutions are formed.

Stirring at rt is continued for about 1 h until all sulphur has dissolved. The

solution is then transferred into the dropping funnel and added over 30 min to

a mixture of 0.22 mol of freshly distilled acetyl bromide or 0.25 mol of ethyl

chloroformate, and 200 ml of Et2O. During, and for 30 min after this addition,

the temperature of the mixture is maintained between –30 and –40 �C.

The cooling bath is then removed and the temperature allowed rising to

0 �C. Ice water (100 ml) is then added with vigorous stirring and cooling at

� 0 �C. The layers are then separated and extraction with Et2O is carried out

(Note 1). After drying over MgSO4, the solvent is removed under reduced

pressure. The remaining lachrymatory liquid is first distilled at <0.5 Torr,

using a very short column and the distillate collected in a single receiver

cooled below –30 �C (Figure 1.10). Redistillation through a 20-cm Vigreux

column gives the desired products (Note 2).

Examples: S-(1-hexynyl)ethanethioate, BuC�CSC(¼O)Me, bp 100 �C/10

Torr, yield� 50%; S-(1-butynyl)O-ethyl)carbonothioate, EtC�CSC(¼O)OEt,

bp 88 �C/10 Torr, yield �55%.

Notes

1. Since the products are water sensitive [12] (BuC�CSC(¼O)Me is converted

into S-(2-oxohexyl) ethanethiolate, BuC(¼O)CH2SC(¼O)Me), the work-

up should be carried out without delay.

2. Part of the sulphur is converted into Li2S, while a corresponding part of

RC�CLi remains in the reaction mixture. With acetyl chloride, MeCOCl,

and ethyl chloroformate, ClCOOEt, 3-alkyn-2-ones, RC�CCOMe, and

ethyl 2-alkynoates, RC�CCOOEt, respectively, are formed. Careful dis-

tillation is necessary to separate these more volatile by products from the

desired compounds. Too strong heating during the distillation should be

avoided as the compounds have limited thermal stability.

8.2.8 1-Propynyl trimethylsilyl sulphide from lithiumpropynethiolate and chloro(trimethyl)silane



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8.2.8.1 Procedure [13,14]

A solution of � 0.20 mol of lithium propynethiolate is prepared from 6.4 g of

dry, powdered sulphur and a suspension of 0.20 mol of propynyllithium (exp.

8.2.6 and Chapter 3, exp. 3.9.4) in 126 ml of hexane and 140 ml of Et2O. The

brown solution is added dropwise over 45 min to a mixture of 0.30 mol (excess)

of freshly distilled chloro(trimethyl)silane and 100 ml of Et2O (Note 1) cooled

between –30 and –40 �C. The cooling bath is then removed and the temperature

allowed rising to 10–15 �C. The solvent and other volatile components are

removed under reduced pressure. The bath temperature should not exceed

30 �C during this operation. The remaining dark brown liquid is then subjected

to vacuum distillation (P<1 Torr), collecting the volatile product in a single

receiver cooled below –50 �C (Note 2). Careful redistillation of the contents

of the receiver through an efficient column gives the desired product, bp

50 �C/12 Torr, in � 55% yield (Note 3).

Notes

1. If the addition is carried out in the normal sense, some dimer of the

thioketene 2-(trimethylsilyl)-1-propene-1-thione, MeC(SiMe3)¼C¼S, a

dithiole derivative, is formed.

2. Since the silyl sulphide is very water-sensitive, all glassware should be dried

carefully.

3. In the cases of higher boiling compounds a small amount of paraffin oil

should be added prior to the distillation. The oil serves as a heat conductor

in the last stage of the distillation, when mainly salt is present in the

distillation flask.

8.2.9 Methyl 1-propynyl sulphoxide from propynyllithiumand methanesulphinyl chloride


8.2.9.1 Procedure

Methanesulphinyl chloride [15] (0.20 mol) is added over 15 min to a suspension

of 0.20 mol of propynyllithium in 150 ml of THF and 126 ml of hexane


[13.1.2004–10:01pm] [175–190] [Page No. 185]


(Chapter 3, exp. 3.9.4) with cooling between –60 and –80 �C (cooling in a bath

with liquid N2 allows a quick addition). Ten minutes after this addition, the

reaction mixture is poured into 100 ml of water. After vigorous shaking,

the layers are separated and the aqueous layer is extracted ten times with

small portions of chloroform. The combined organic solutions are dried

over MgSO4, after which the solvent is removed in vacuo. The remaining

liquid is distilled at oil pump pressure to give methyl-1-propynyl sulphoxide,

bp � 70 �C/0.5 Torr, in � 75% yield.

Methylsulphonyl chloride, MeSO2Cl, and 4-methylbenzenesulphonoyl

chloride give low to moderate yields of the sulphones RC�CSO2Me and

RC�CSO2–C6H4–4-Me. Part of the sulphonyl chloride reacts with the lithium

alkynylide to give a chloroalkyne. A more succesful method to prepare acety-

lenic sulphones involves oxidation of acetylenic sulphides with peracids (see

Chapter 20, Section 20.9).

8.2.10 Di(1-alkynyl) sulphides and di(1-alkynyl) sulphoxides fromalkynyllithium and sulphur dichloride or thionyl chloride

Scale: 0.10 molar (SCl2 or SOCl2); Apparatus: Figure 1.1, 500 ml

8.2.10.1 Procedure [4]

Freshly distilled (bp 58–62 �C/760 Torr) sulphur dichloride (0.10 mol, diluted

with 30 ml of Et2O, cooled to –40 �C) or thionyl chloride (0.10 mol, freshly

distilled, diluted with 30 ml of Et2O) is added dropwise over 10 to 15 min to a

vigorously stirred suspension or solution of 0.20 mol of alkynyllithium (Chapter

3, exp. 3.9.4) in 126 ml of hexane and x ml (Note 1) of Et2O. During this

addition, the temperature is kept between –85 and –95 �C by occasional cooling

in a bath with liquid N2, care being taken that no solid layer of solvent is formed

on the bottom of the flask. Ten minutes after the addition, the suspension is

poured into yml (Note 2) of ice water. After vigorous shaking and separation of

the layers, the aqueous layer is extracted three times with Et2O (in the case of the

sulphide) or three times with dichloromethane (in the case of the sulphoxides).


[13.1.2004–10:01pm] [175–190] [Page No. 186]


The organic solutions are dried (without preceding washing) over MgSO4,

and then concentrated in vacuo. In the case of the sulphides, the remaining

liquid is subjected to a high-vacuum distillation (P<0.5 Torr) and the distillate

collected in a strongly cooled single receiver (Figure 1.10,Note 3). Redistillation

gives the following sulphides: di(1-propynyl) sulphide, (MeC�C)2S, bp� 30 �C/

0.2 Torr, yield � 65%; di(1-butynyl) sulphide,(EtC�C)2S, bp � 45 �C/0.2 Torr,

yield � 70%; bis(3,3-dimethyl-1-butynyl) sulphide, (t-BuC�C)2S, bp � 50 �C/

0.2 Torr, yield �75%; bis[2-(trimethylsilyl)ethynyl] sulphide, (Me3SiC�C)2S,

bp � 55 �C/0.2 Torr, yield � 70%.

Di(1-propynyl) sulphoxide, (MeC�C)2S¼O, mp 69.5–70 �C, di(1-butynyl)

sulphoxide, (EtC�C)2S¼O, (oil, not distilled), and bis(3,3-dimethyl-1-butynyl)

sulphoxide, (t-BuC�C)2S¼O, mp 47–47.5 �C are obtained in � 70% yields.

The solid compounds are crystallised from a 1:1 mixture of Et2O and pentane.

Attempts to prepare the corresponding sulphones from the reaction with

sulphuryl chloride failed

Notes

1. x ¼ 200 in the cases of the sulphoxides and 400, 300 and 200, respectively,

in the cases of the sulphides R ¼Me, Et and t-Bu (or Me3Si). When THF is

used instead of Et2O, yields of the sulphides R ¼Me or Et are � 30% only.

A possible explanation is that the very base-sensitive di(1-alkynyl) sul-

phides (MeC�C)2S and (EtC�C)2S are attacked by alkynyllithium. In

the more polar THF this attack is more serious than in Et2O while the

solubility of RC�CLi in Et2O is much less.

2. y ¼ 150 in the case of the sulphides and 50 in the case of the sulphoxides.

3. The viscous, brown residue may undergo vigorous decomposition. This

explains the necessity of a first flash distillation at very low pressure

with moderate heating.

8.2.11 Di(1-alkynyl) tellurides from tellurium tetrachlorideand lithium acetylides

Scale: 0.05 molar (TeCl4); Apparatus: Figure 1.1, 500 ml


[13.1.2004–10:01pm] [175–190] [Page No. 187]


8.2.11.1 Procedure [16]

A cold (–40 �C, made immediately before the addition) solution of 0.05 mol of

TeCl4 in 40 ml of THF is added quickly with cooling at –25 �C to a solution of

0.25 mol (excess) of alkynyllithium (Chapter 3, exp. 3.9.4) in 160 ml of hexane

and 100 ml of THF. The light brown solution is heated for 40 min at 45 to 50 �C

(for R ¼ Me or Et) or 1 h at � 60 �C (if R ¼ t-Bu and Me3Si), then cooled to

0 �C and treated with 200 ml of deoxygenated ice water (tellurium compounds

are very air-sensitive). After extraction of the aqueous layer with pentane and

drying of the organic solution over magnesium sulphate, the solvents are

removed under reduced pressure. Distillation of the remaining liquids through

a very short column gives the following compounds: di(1-propynyl) telluride,

bp 110 �C/15 Torr, mp 50–52 �C after crystallisation from pentane, yield

�40%; di(1-butynyl) telluride, bp 125 �C/15 Torr, yield �55%; di(1-pentynyl)

telluride, bp 68 �C/0.07 Torr, yield �70%; di(3,3-dimethyl-1-butynyl) telluride,

bp 130 �C/15 Torr, mp 62–64 �C, yield �60%; bis(2-trimethylsilylethynyl) tell-

uride, bp 135 �C/15 Torr, yield �60%.

8.2.12 Bis(alkylthio)acetylenes from sodium acetylideand alkyl thiocyanates


8.2.12.1 Procedure [17]

Methyl thiocyanate or ethyl thiocyanate (0.30 mol) is added dropwise over

15 min to a solution of 0.30 mol of sodamide in 350 ml of liquid ammonia

(Chapter 3, exp. 3.9.1, care should be taken to stop introduction of acetylene as

soon as the blue colour of dissolved sodium has vanished). The ammonia is

allowed to evaporate (Figure 1.7) or is removed by placing the flask in a bath

at 35–40 �C. After addition of 300 ml of water extraction with Et2O or pentane

is carried out. The organic solution is concentrated under reduced pressure

after drying. The bis(alkylthio)acetylenes, R ¼ Me, bp 72/10 Torr, and R ¼

Et, bp 90 �C/10 Torr, are obtained in excellent yields.

8.2.13 Bis(alkylthio)acetylenes from lithium chloroacetylideand dialkyl disulphides


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8.2.13.1 Procedure

A gently (Note) stirred solution of 0.20 mol of lithium amide in 250 ml of liquid

ammonia is cooled to –50 �C. A mixture of 0.10 mol of 1,2-dichloroethene

(mixture of isomers) and 40 ml of Et2O is added dropwise over 10 min while

introducing nitrogen (500 ml/min, Note). After an additional 10 min (at

� –40 �C) 0.10 mol of dialkyl disulphide dissolved in 30 ml of Et2O is added

dropwise over 15 min without further cooling. After 2 h the thermometer-

outlet combination is removed and 20 g of powdered ammonium chloride is

added over 10 min. The ammonia is allowed to evaporate (Figure 1.7). After

addition of 150 ml of water extraction with Et2O or pentane is carried out.

The extracts are dried and concentrated under reduced pressure, after which

the products are isolated in high yields by distillation in vacuum (for bp see

preceding exp).

Note

If stirring is carried out vigorously, the solution of LiC�CCl may splash

against the upper part of the flask and in the necks where it cannot react

with the disulphide in the next step. During the aqueous work-up the highly

explosive chloroacetylene may be formed from this unconverted LiC�CCl. If

no inert gas is introduced, moisture and air can enter and as a result small

amounts of chloroacetylene will be formed.

REFERENCES

1. L. Brandsma, H. J. T. Bos and J. F. Arens, in Chemistry of Acetylenes (ed. H. G. Viehe).

Marcel Dekker, New York, 1969, p. 751.

2. Unpublished observations and results from the author’s laboratory.

3. J. R. Nooi and J. F. Arens, Recl. Trav. Chim., Pays-Bas 80, 244 (1961).

4. W. Verboom, M. Schoufs, J. Meijer, H. D. Verkruijsse and L. Brandsma, Recl. Trav. Chim.,

Pays-Bas 97, 244 (1978).

5. S. Hoff, L. Brandsma and J. F. Arens, Recl. Trav. Chim., Pays-Bas 87, 1179 (1968).

6. X. Creary, J. Am. Chem. Soc. 99, 7632 (1977).

7. A. Haces, E. M. G. A. van Kruchten and W. H. Okamura, Tetrahedron Lett. 23, 2707 (1982).

8. M. Cinquini, S. Colonna and C. J. M. Stirling, J. Chem. Soc., Chem. Comm., 256 (1975).

9. H. J. Backer, Recl. Trav. Chim., Pays -Bas 67, 894 (1948).

10. L. Brandsma, Recl. Trav. Chim., Pays-Bas 83, 307 (1964).

11. H. E. Wijers, P. P. Montijn, L. Brandsma and J. F. Arens, Recl. Trav. Chim., Pays-Bas 84,

1284 (1965).

12. W. Drenth and G. H. E. Nieuwdorp, Recl. Trav. Chim., Pays-Bas 88, 307 (1969).

13. R. S. Sukhai, J. Meijer and L. Brandsma, Recl. Trav. Chim., Pays-Bas 96, 179 (1977).


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14. S. J. Harris and D. R. M. Walton, J. Chem. Soc., Chem. Comm., 1008 (1976).

15. I. B. Douglass and R. V. Norton, J. Org. Chem. 33, 2104 (1968).

16. R. W. Gedridge, Jr., L. Brandsma, R. A. Nissan, H. D. Verkruijsse, S. Harder, R. L. P. de

Jong and C. J. O’Connor, Organometallics 11, 418 (1992).

17. H. D. Verkruijsse and L. Brandsma, Synthesis, 818 (1991).

18. A. A. Petrov, S. I. Radchenko, K. S. Mingaleva, I. G. Savich and V. B. Lebedev, Zh. Obsch.

Khim. 34, 1899 (1964).

19. A. A. Petrov, I. A. Maretina and N. A. Pogorzhel’skaya, Zh. Org. Khim. 11, 1757 (1966).

20. R. Raap and R Micetich, Can. J. Chem. 46, 1057 (1968).

REFERENCES 189

synthesis of acetylenes, allenes and cumulenes || sulphenylation and related reactions

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