Visible-light-enabled spirocyclization of alkynes leading to 3-sulfonyl and 3-sulfenyl azaspiro[4,5]trienones

Abstract

A mild and convenient visible-light-induced method has been developed for the construction of 3-sulfonyl and 3-sulfenyl azaspiro[4,5]trienones through metal-free difunctionalization of alkynes with sulfinic acids or thiols at room temperature. The present protocol simply utilizes visible light as the safe and eco-friendly energy source, and inexpensive and non-toxic organic dyes (Eosin Y and Na₂-Eosin Y) as photocatalysts providing various sulfur-containing azaspiro[4,5]trienones in moderate to good yields.