Rhodium-catalyzed formal (3 + 3) transannulation of 1,2,3-thiadiazoles and vinyloxiranes

Abstract

A rhodium-catalyzed formal (3 + 3) transannulation of 1,2,3-thiadiazoles and vinyloxiranes is realized, accessing to 2,3-dihydrothiopyran-4-ones in moderate to good yields. The transannulation is a tandem sequence of the Lewis acid-catalyzed Meinwald rearrangement of vinyloxiranes and formal (3 + 3) transannulation of formed alk-2-enals and in situ generated 1-thia-2-rhodacyclobutenes from 1,2,3-thiadiazoles, rather than a thioacyl carbene-induced ring expansion of oxiranes, different from the reaction of acylcarbenes with oxiranes and thiiranes.