Radical addition reactions sulfenylation

In this chapter, we discuss reactions that either add adjacent (vicinal) groups to a carbon-carbon double bond (addition) or remove two adjacent groups to form a new double bond (elimination). The discussion focuses on addition reactions that proceed by electrophilic polar (heterolytic) mechanisms. In subsequent chapters we discuss addition reactions that proceed by radical (homolytic), nucleophilic, and concerted mechanisms. The electrophiles discussed include protic acids, halogens, sulfenyl and selenenyl reagents, epoxidation reagents, and mercuric and related metal cations, as well as diborane and alkylboranes. We emphasize the relationship between the regio-and stereoselectivity of addition reactions and the reaction mechanism. 

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-... 

Kropp and coworkers have been concerned with systems in which homolysis is followed by rapid electron transfer, such as the photolysis of certain alkyl halides [55]. Photolysis of the norbomyl phenyl sulfoxide 110 was examined. The notion was that sulfide photolysis is usually homolytic, but the sulfinyl radical is more electronegative than the sulfenyl (thiyl) radical, which might assist in electron transfer reactions. Thus, it was thought, ionic reactivity might be observed. In addition to inversion of the sulfur center and deoxygenation (yide infra), norbomane 111 and norbomene 112, both presumed to... 

The reaction of the thiazoline sulfur with iodine depended upon the side chain and reaction conditions (Micetich and Morin, 1976). The thiazoline (162) reacted to give complex A or B depending upon the stoichiometry. Addition of water to complex A gave the symmetrical disulfide (246) which on further iodination yielded the 3-iodocepham (247). Complex B with water gave 247 directly. Other workers have reported catalytic effects of free radical initiators or heavy metal oxides in this transformation (W. Germ. Patent 2,534,811 Micetich and Morin, 1977). It was postulated that the sulfenyl iodide intermediate (248) was obtained on aqueous treatment of the original complexes which then spontaneously cyclized to the cepham derivative. 

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