Trialkylsilyl substituent effect on ring expansion of chloroalkyl dithioketals. An easy method for the preparation of 2-trialkylsilyl-1,5-dithiacyclooct-2-enes

Silylated 2- and 3-chloroalkyl dithioketals were prepared from corresponding 2-lithio dithioketals with 1,2- and 1,3-dihaloalkanes. The functionalized 1,3-dithianes underwent an easy ring expansion reaction into 1,5-dithiacyclooct-2-enes in the presence of basic alumina in refluxing petroleum ether.