A 4 + 2 annulation with 1,3-dienes, AgSCF3, and KI has been established, affording a variety of CF3S-substituted 2H-thiopyrans with high chemo- and regioselectivities. The intermediate (CF3S)2C═S is generated in situ via the reaction of AgSCF3 with KI under mild conditions. This method features the advantages of readily available starting materials, broad substrate scope, operational simplicity, and high atom economy.
Guo et al. (Thu,) studied this question.