Ethyl 2-amino-4H,5H,6H-cyclopenta[b]thiophene-3-carboxylate

Ethyl 2-amino-4H,5H,6H-cyclopenta[b]thiophene-3-carboxylate (CAS 4815-29-6) is a strategically fused bicyclic thiophene derivative engineered for heterocyclic construction and medicinal chemistry applications. Distinct from monocyclic aminothiophene esters, this molecule features a cyclopentane ring fused to the thiophene core, creating a rigid 5,5-bicyclic architecture that enhances metabolic stability and target binding affinity. The classic 2-amino-3-ester substitution pattern facilitates efficient condensation cyclization with 1,3-dielectrophiles (e.g., formamidine acetate, urea) to construct fused thienopyrimidines, thienopyridines, and other polyheterocyclic systems prevalent in kinase inhibitors. The saturated carbocyclic ring provides conformational constraint and improved lipophilicity compared to aromatic benzo-fused analogs, while the ethyl ester moiety offers versatile handles for hydrolysis or transesterification. This intermediate is particularly valuable for constructing ATP-mimetic kinase inhibitors, CNS-penetrant scaffolds, and agrochemical actives where the tetrahydrocyclopentathiophene motif optimizes physicochemical properties. Manufactured with purity ≥98% under controlled conditions, it supports drug discovery programs requiring modular access to rigid sulfur-containing heterocyclic architectures.