Remarkable Mechanism of the Reaction between Mixed Phosphonium-Iodonium Ylides and Acetylenesстатья
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Дата последнего поиска статьи во внешних источниках: 9 декабря 2020 г.
Аннотация:Reactions of mixed phosphonium-iodonium ylides with nitriles and acetylenes allow for the synthesisof not easily accessible and novel heterocyclic compounds in a simple, one-pot, metal-free system. Theresults of the mechanistic investigation of the reaction of the phosphonium-iodonium ylides with acetylenesby means of spectrophotometry, EPR and NMR spectroscopy are discussed in this review. This investigationallows to account for unusual regularities of these reactions: induction time, acid catalysis, chemicallyinduced dynamic nuclear polarization effect (CIDNP) observed in several systems, and others. The radicalcharacter of the initiation of the reaction as a result of acid catalysis of the ylides decomposition on radicalsand the participation of radical intermediates in the formation of all target products have been unambiguouslyestablished. The mechanism of generation of radical pairs in CIDNP was suggested, and the role of microheterogenietyof the ylide solutions in methylene chloride was substantiated. On the basis of the study of the reaction mechanism,the conditions for the increase in the yields of new heterocyclic compounds can be optimized