Reactions of thiobenzoylketene S,N-acetals with silyl enol ethers of cyclic ketones in the presence of desilylating reagents: formation and desulfurization of thienolactams

Abstract

Medium-sized thienolactams can be directly prepared from thiobenzoylketene S,N-acetals, Hg(OAc)₂, and silyl enol ethers of cyclic ketones, and either TBAF or TASF. However, by adding either water or alcohol to the foregoing mixture, 3-methylamino-5-phenylthiophenes, in which the ω-position of long-chain alkanoic acids and alkanoic esters are bonded to C-2 of the thiophene ring, can be obtained albeit in low yields. Sequential treatment of the thienolactams with Raney nickel and Adam's catalyst results in completely reductive desulfurization of thienolactam molecules.