Divergent Synthesis of Benzo[4,5]imidazo[2,1- b ][1,3]thiazines and α-Trifluoromethyl-β-arylthio Tertiary Alcohols from 2-Mercaptobenzimidazoles and α-CF 3 Alkenes

An efficient and metal-free approach for the divergent synthesis of 2-fluoro-3-aryl-4 -benzo[4,5]imidazo[2,1- ][1,3]thiazines and -trifluoromethyl- -arylthio tertiary alcohols from 2-mercaptoimidazoles and -CF alkenes has been developed. The chemoselectivity was well controlled by base or light; a series of 2-fluoro-3-aryl-4 -benzo[4,5]imidazo[2,1- ][1,3]thiazines were afforded base-mediated sequential S 2'- and S V-type reactions. Meanwhile, -trifluoromethyl- -arylthio tertiary alcohols could be selectively achieved through visible-light-driven and electron donor-acceptor (EDA) complex-initiated radical cascade thiolation/hydroxylation in the absence of base, transition metal, and external photocatalyst.