Synthesis of thiazoles by desulfurative cyclization/ring expansion cascade reaction of S-azirinyl xanthates: two mechanistically distinct radical pathways

Abstract

S-Azirinyl xanthates were synthesized as novel 2H-azirine derivatives exhibiting dual reactivity toward free radicals. Carbon-, tin-, and silicon-centered radicals initiate a desulfurization/ring expansion cascade of these compounds to form thiazoles in fair to good yields. Radicals can react with azirinyl xanthates either at the nitrogen (stannyl radicals) or sulfur (alkyl and silyl radicals), transforming them into the thiazoles through the intermediate formation of either aziridinyl or thiaazabicyclopentyl radicals, respectively. Both transformations do not involve the degenerative radical transfer and are unprecedented for the radical chemistry of xanthates.