DBU-mediated [4 + 1] annulations of donor-acceptor cyclopropanes with carbon disulfide or thiourea for synthesis of 2-aminothiophene-3-carboxylates.

DBU-mediated [4 + 1] annulations of donor-acceptor cyclopropanes with carbon disulfide or thiourea to form 2-aminothiophene-3-carboxylate derivatives have been discovered. This reaction proceeds via the ring opening of donor-acceptor cyclopropanes to produce a 2-(iminomethylene)but-3-enoate intermediate, followed by the attack of an S-nucleophile for regioselective intermolecular nucleophilic addition, intramolecular S-nucleophilic addition, and final aromatization. A variety of functional groups could be tolerated under the reaction conditions.