Mechanism and Remarkable Features of Photoinduced Cycloaddition of Phenylacetylene to Mixed Phosphonium—Iodonium Ylide

摘要

In recent years, the investigation of the structure and reactivity of an almost uninvestigated class of mixed phosphonium—iodonium ylides allowed us to create novel reagents for organic synthesis on their basis. This class of compounds with several reactive centers exhibits new reactions and opens new routes to the synthesis of not easily accessible and novel heterocyclic compounds [1—3]. Recently, we described two unknown photochemical reactions of mixed phosphonium—iodonium ylides in the presence of compounds with triple bond to give products of pseudo-cycloaddi- tion [4—7]. The direction of the photolysis: depends on the structures of the compounds with a triple bond. Nitriles R1CN afford oxazoles with high yield, PhI being the leaving group [4]. When the reaction occurs between mixed phosphonium—iodonium ylide (1) and acetylenes (2), λ~5-phosphinoline (4), furan derivative (5), PhI (3), and phosphonium salt (6) are formed as a result of the photolysis (Scheme 1; the counterion BF4~-is omitted in Scheme 1 and further on for simplicity) [6, 7]. The relative yield of products 4—6 depends substantially on the structure of acetylene [7].