Counterattack reagent: hexamethyldisilane in a direct synthesis of ketene dithioacetals and 2-trimethylsilyl-1,3-dithiane derivatives from 1,3-dithiane

Abstract

A novel method has been developed for the direct synthesis of ketene dithioacetals and 2-trimethylsilyl-1,3-dithiane derivatives from 1,3-dithiane. Treatment of 1,3-dithiane (1.0 mol equiv.) with BuLi (1.1 mol equiv.), HMPA (4.0 mol equiv.), and Me₃SiSiMe₃(1.1 mol equiv.) produced 2-lithio-2-trimethylsilyl-1,3-dithiane. To this solution was added an aldehyde, ketone, enone, 1-nitroalkene, or organic bromide (1.1–1.2 mol equiv.) in THF to give the desired products (i.e., 7–16) at room temperature in 54–98% yield. In this newly developed ‘one-flask’ method, Me₃SiSiMe₃ acts as a ‘counterattack reagent’.