Synthesis and Reactions of 2,6-Diphenyl-4-(trimethylsilyl)-4H-thiopyran

Article abstract of DOI:10.1021/jo00343a015

The title compound 3 was synthesized by trimethylsilyl chloride quenching of 2,6-diphenyl-4-lithio-4H-thiopyran (7), which was obtained by direct lithiation (n-BuLi) of either the 4H-thiopyran 10 or the 2H isomer 6.Compound 6 was readily prepared in one step from the reaction of 2,6-diphenyl-4-hydroxy-4H-thiopyran (5) with NCS in 74percent yield.Compound 3 was metalated to give 12 in 80-85percent yield by using a combination of n-BuLi and t-BuOK in THF at an internal temperature slightly below -20 deg C.The successful reaction of 12 with a variety of ketones and aldehydes provides an alternative synthesis of the Δ⁴-2,6-diphenyl-4H-thiopyrans 16.The scope and limitation of this Peterson-type reaction of 12 is compared with those of the corresponding Wittig-Horner reagent 2.