Synthesis and transformations of stereoisomeric ethyl 2-isothiocyanato-1-cyclopentanecarboxylates

Ethyl cis- and trans-2-isothiocyanato-1-cyclopentanecarboxylates 2 and 7 we re prepared by the reaction of the corresponding alicyclic ethyl 2-amino-1- carboxylates and thiophosgene. The cis-isothiocyanato compound 2 underwent ring closure with amines in one or two steps, resulting in 3-substituted-ci s-2-thioxocyclopenta[d]pyrimidin-4-ones 3a-g. The trans isomer 7 failed to cyclize, but gave carboxamide 8a,b or thiourea ester derivatives 9a,b.