Sulfenyl compounds

However, a few thiols (cysteine, N-acetylcysteine and thiosalicylic acid) also react with organic nitrates to release NO by another process that is difficult to discern. It could be that the nitrite reacts with a thiol to give an S-nitrosothiol, a ready source of NO, but nitrosation is unlikely to occur at biological pHs. Another possible route to NO involves formation of a thionitrate by trans-esterification [59] (Eq. (12)). This species could then decompose to give NO via an intermediate sulfenyl compound [60] (Eq. (13)). 

The reactions of thiosulfonates shown in general form in (167), and which constitute the majority of their chemistry, are, of course, substitution reactions at a dico-ordinate, or sulfenyl, sulfur. Substitutions of this type occur widely and with great frequency in the chemistry of all types of sulfenyl compounds. Because of their extreme importance in the chemistry of both thiolsulfonates and other sulfenyl derivatives, it is appropriate that we now review some of the major features regarding their mechanism that have emerged from the study of such reactions with various sulfenyl derivatives. 

Electrophilic addition of sulfenyl compounds at carbon-carbon double bonds, extensively studied and reviewed2,4 715 106, finds numerous synthetic applications owing to the regio- and stereoselectivity of the addition26. The most common types of agents for the electrophilic addition of sulfur to double and triple bonds are sulfenyl halides (RSX,... 

Disulfane Starting materials Thiocarbonyl Sulfenyl compound halide Reaction time (hr) Yield (%)... 

Complete regiodirection by the NHCOOR for 4-sulfurated (sulfenyl, sulfmyl, and sulfonyl) -1,3-butadiene-1 -carbamates in their Diels-Alder reactions [182] is quite natural. The case at issue might be the sulfenylated compounds, but we must remember that divalent sulfur can act as an acceptor. 

Although very few studies of free-radical reactions of sulfenyl compounds have as yet been reported, irradiation with ultraviolet light enhances the rate of addition of CI3CSCI to olefins.218 Evidence for free-radical behavior is found in the easy decompositions which are observed for RSC1 under irradiation, e.g., the conversion of methanesulfenyl chloride to chloromethanesulfenyl chloride287 under the influence of sunlight. In the photoinitiated chlorination reaction with trichloro-... 

They are believed to exert their effects by reaction of cellular thiols either with the intact compounds or with thiophosgene evolved by breakdown. This non-specific mode of action may be the reason why resistance to the sulfenyl compounds has not developed. 

Finally, an example of the reactions at a dicoordinated sulfenyl sulfur is presented. The reactions of (alkoxydichloromethyl)(chlorocarbonyl)polysulfanes (11) with Af-methylani-line in CHCI3130 are rationalized by a carbamoyl route where the alkoxydichloromethyl group loses an alkyl chloride as a masked acid chloride, or by a sulfenyl route which reflects fragmentation of the (alkoxydichloromethyl)polysulfanyl compound into the corresponding alkoxy(thiocarbonyl) and sulfenyl compounds 11 (Scheme 15). 

Haas, A., Terfluoropseudohalides and the Chemistry of Chlorofluoromethyl-sulfenyl Compounds," In New Pathways Inorg. Chem. Ebsworth, E. A. V., Ed. University Press Cambridge, England, 1968 p 87. 

Organocatalysis One of the most diHicult aspects in the development of asymmetric sulfenylation methods for carbonyl compounds is to ensure the stability of the resulting a-sulfenylated compounds. Based on the pioneering study by Kuehne of reactions of enamines with arylsulfonyl chloride, the catalytic asymmetric a-sulfe-nylation has been investigated by enamine catalysis. An... 

Such a reversible blocking of the 2-position by sulfenylation was of particular interest in the synthesis of bromo-derivatives of indolyl-3-propionic acid. Specific bromination or nitration of the benzene ring of an indole is normally difficult to achieve, since the pyrrole ring also will react with electrophilic reagents. As an example, 5-bromoindole-3-propionic acid has been prepared using this reversible protection, that is by bromination of the 2-sulfenylated compound and removal of the arylthio group by the two consecutive reactions with NBS and NaBKi (727). 

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