Benzylmercaptane

The C-S bond in purine derivatives undergoes cleavage under mild conditions by nucleophilic agents such as benzylmercaptan or glutathione in dimethylformamide with a phosphate buffer of pH 6.5 (277). The salt (110) of dithiazolylsulfide heated at 190 C yields the A-4-thiazo-line-2-thione (112) and 2-chlorothiazole (111) (Scheme 56) (278-280). 

Benzylmercaptan reacts with diacetylenes 57 under base-catalyzed conditions in aregio- and stereoselective fashion to form diadducts Z,Z-l,4-di(benzylthio)buta-1,3-dienes (59). In this case, monoadducts 58 can be isolated (96T12677). The reaction with r-butylmercaptans gives good results for diacetylenes with aromatic substituents. 

B Preparation of Benzyithiomethyi-6-Chioro-7-Suifamyi-3,4-Dihydrobenzothiadiazine-1,1-Dioxide—A. mixture of 3-(chloromethvl)-6-chloro-7-sulfamvl-3,4-dihydrobenzothiadiazine-1,1-dioxide (0.02 mol) and benzylmercaptan (0.024 mol) in 20 ml of 10% sodium hydroxide and 20 ml of dimethylformamide is stirred at room temperature for 6 hours. 

The best evidence for the photolytic decomposition of mercaptans and disulfides into free radicals involves photoinitiation of polymerization of olefins. Thus, photolysis of disulfides initiates the copolymerization of butadiene and styrene,154 as well as the polymerization of styrene207 and of acrylonitrile.19 Thiophenol and other thiols promote polymerization upon ultraviolet irradiation.19 Furthermore, the exchange of RS-groups between disulfides and thiols is greatly accelerated by light. Representative examples are benzothiazolyl disulfide and 2-mercapto-thiazole,90 tolyl disulfide and p-thiocresol, and benzyl disulfide and benzylmercaptan.91 The reaction probably has a free radical mechanism. Similar exchange reactions have been observed of RS-groups of pairs of disulfides have been observed.19... 

Reaction between benzylmercaptans and haloacetic acids yield benzylmercaptoacetic acids (57) which, via their acid chlorides, undergo an intramolecular Friedel-Crafts cyclization to produce isothiochromanones as in Eq. (24).233-235 Attempts to cyclize 57 with sulfuric acid,... 

In this sequence, substitution by 1 mol of dimethylamine first replaces the benzylmercaptan leading to 5-acetyl-2-dimethylamino-6//-l,3-thiazine (197). The thiazine then undergoes attack by dimethylamine excess at C-6, leading to the thiourea (198). The benzylmercaptan liberated in the first reaction may act as a nucleophile (BzS",H2NMe2+), and a different thiourea substituted by dimethylamino and benzylthio groups is obtained. The action of pyrrolidine on 1,3-thiazine-4-ones (194) can be seen as a Michael addition followed by elimination of H2S. In acidic media, the linear compound obtained is cyclized to the pyrimidone (200) (Scheme 80)... 

Fig. 8. Recording of t—E curves during the course of a reaction Reaction of S-ben-zyl-isothiuronium chloride with hydroxide and carbonate ions in carbonate buffer pH 9.7. Initial concentration of S-benzylisothiuronium chloride 4 x 10 4M. Anodic waves of benzylmercaptan formed were recorded after intervals given in the polarogram. Curves starting at — 1.0 V towards more positive potentials, S.C. E., 200 mV/absc., h = 70 cm, full scale sensitivity 2.2 p.A...

Dibenzylsulfide. Figure 13 shows the identified products of aerobic and anaerobic metabolism of dibenzylsulfide. Babienzien et al. (68) incubated this substrate with a mixed population of aerobic bacteria and detected several water-soluble organic products. However, only benzylmercaptoacetic acid was identified. Kohler et al. (49) incubated dibenzylsulfide with a selected strain of Desulfovibrio utilizing molecular hydrogen under anaerobic conditions where sulfate served as the terminal electron acceptor. Toluene and benzylmercaptan were identified as metabolites. In addition, 35S-sulfide was found in cultures incubated with 35S-dibenzylsulfide. 

Figure 13. Microbial metabolites of dibenzylsulfide found in studies under aerobic and anaerobic conditions. (I) benzylmercaptoacetic acid, (II) toluene, (III) benzylmercaptan.

An account has also been given of the reaction between benzylmercaptan and cis-benzene trioxide.With a-mercapto esters, p-substituted phenyloxiranes undergo normal opening, without being affected by the substituents on the benzene ring. Chalcone oxides react with mercaptan with accompanying C-C bond cleavage (Eq. 308). ... 

Amino-3-cyano-5-(benzylthiomethyl)pyrazine 1-oxide has been prepared from j3-bromopyruvaldoxime, benzylmercaptan, and aminomalononitrile tosylate in propan-2-ol (542). 

Water, benzylmercaptan, and amines were used as initiators. The polymers had number-average degrees of polymerization up to 50. 

One problem of prime importance is the reliable determination of the number of residues of ,/3-unsaturated amino acids in proteins. Direct amino acid analysis subsequent to total hydrolysis of proteins is not feasible. The ,/3-unsaturated amino acids are subject to degradation with the formation of amide (ammonia) and -keto-acid. The numbers and types of ,/3-unsaturated amino acids in nisin (1) and subtilin (10) and in the fragments of the two peptides were, nevertheless, determined by amino acid analysis, only, however, after the addition of mercaptan across the double bonds of dehydroalanine and dehydrobutyrine (19). Using benzylmercaptan, the addition products are S-benzylcysteine (from dehydroalanine) and /3-methyl-S-benzylcysteine (from dehydrobutyrine). The two thioether amino acids are eluted from ion exchange columns of the amino acid analyzer free from interference by other amino acids... 

Figure 16. Determination of the type and quantity of a,/3-unsaturated amino acids in subtilin—note the elution positions of the addition products of benzylmercaptan to dehydroalanine and dehydrobutyrine S-benzylcysteine ana / -...

It was found that much better yields are obtained if the vinylpyridine is first converted into the corresponding benzyl pyridylethyl sulfide (by reaction with benzylmercaptan), followed by pyrolysis of the latter over glass helices at high temperature with either nitrogen or hydrogen sulfide as carrier gas37 I Eq. (16)]. 

In order to ensure that the reactivity of cjj-1,2-dihydroxy-1,2-dihydroacronycine diesters towards nucleophilic agents was similar to that of acronycine and precocene epoxides, the diester was reacted with benzylmercaptan (2i) in acidic medium. The cis and trans adducts 7 and with the sulfur atom linked to the benzylic position of the pyranyl ring were obtained in almost quantitative yield under these conditions (58). 

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