A One-Pot Assembly of Fully Substituted Alkyl 5‑Aminothiophene-2-carboxylates from Allenes, Isothiocyanates, and Alkyl 2‑Bromoacetates

A novel simple approach to highly functionalized multisubstituted thiophenes such as alkyl 4-alkoxy-5-amino-3-methylthiophene-2-carboxylates through the one-pot sequential reaction of α-lithiated alkoxyallenes with isothiocyanates and alkyl 2-bromoacetates has been discovered. The process proceeds quickly (30–45 min) via in situ formation and intramolecular cyclization of alkyl 2-[(2-alkoxybuta-2,3-dienimidoyl)­sulfanyl]­acetates (1-aza-1,3,4-trienes)