Preparation and structure of some cis-fused ureas: cis-perhydrothieno-[3,4-d]imidazol-2-one SS-dioxides

Abstract

A general route to the title compounds has been developed. This involves cyclisation of 2,3-dihydro-3-ureidothiophen SS-dioxides (20) with base. Both symmetrically and unsymmetrically substituted cis-fused ureas (2) can be prepared. A similar base-induced reaction of the corresponding 3-carbamoyl-2,3-dihydrothiophen SS-dioxides led, via the corresponding cyclic carbamates (8), by a route involving elimination and double-bond migration, to the corresponding 4-amino-2,3-dihydrothiophen SS-dioxides (11).