Sulfenimines disulfides

Bromide and iodide ions are not only effective as redox catalyst in the indirect electrochemical formation of carbon-hetero atom bonds but also of hetero-hetero atom bonds. Thus, the nitrogen-sulfur bond in sulfenimides (Eq. (53) Table 4, No. 33) and sulfenimines (Eq. (54) Table 4, No. 34) can be generated. The electrogenerated active bromine species forms a positively polarized sulfenyl intermediate from disulfides. 

Direct transformation of a/p/w-aminoalkanoates 27 to the corresponding sulfenimines 29 by electrolysis with disulfide 28 in a CHjCyHjO—MgBr2—(Pt) system has been developed (Scheme 2-9)22). The procedure can be applied to the sulfenylation of C-6/C-7 amino groups of penicillins and cephalosporins 30 (Scheme 2-10). 

When mixtures of a-aminoalkanoates and disulfides are electrolyzed in CH2CI2-H20-MgBr2 using Pt electrodes, they are transformed directly into sulfenimines [Eq. (24)] [54]. Amino groups of penicillin and cephalosporin are conveniently sulfanylated by this procedure. 

The treatment of a disulfide with ammonia, silver nitrate, and a ketone is a general one-step synthesis of sulfenimines.13 The disulfide 5, in an intramolecular reaction, affords13 the 1,2-benzisothiazole 6. 

Similar indirect anodic oxidations of various fluoropropylamines and diphenyl disulfide in two-phase systems such as CH2Cl2-water provide useful fluorinated sulfenimines as shown in Eq. 66. ... 

In related work, Saito and Hiraoka (1977a) synthesized some unusual dimeric sulfenimines (221-225) by reaction of 7-aminocephem 220 with thionyl chloride and triethylamine. A major coproduct in these transformations was dimeric cephem 226. Acylation of this material with phenylacetyl chloride gave a dimeric amide identical to a substance prepared earlier by Yanagi-sawa and Nakao (1976) [vide supra). Treatment of 221 with methanol and triethylamine produced the monomethoxylated product (227) in 74% yield. Bis-methoxylation was not achieved, even under forcing conditions. In the case of disulfide 222, similar conditions led to 7a-methoxy-7-deacetoxyce-phalosporanic acid methyl ester (27%). The mode of desulfurization is unclear at this time. Related chemistry involving nitrogen-sulfiir bonds was discussed by Sankyo researchers in a subsequent paper (Saito and Hiraoka, 1977b). 

---