SUBSTITUENT EFFECTS IN THIOPHENE COMPOUNDS. I. 1H NMR AND IR STUDIES IN METHYL (SUBSTITUTED 2-THIOPHENECARBOXYLATE)S.

Article abstract of DOI:10.1246/bcsj.56.2463

The **1H NMR spectra and the IR carbonyl stretching frequencies of methyl (3-, 4-, and 5-substituted 2-thiophenecarboxylate)s have been reported. Good linear correlations between the chemical shifts of the ring protons in methyl (4- and 5-substituted 2-thiophenecarboxylate)s and those of the corresponding protons in substituted thiophenes were observed. The coupling constants in methyl (substituted 2-thiophenecarboxylate)s gave good correlations against the corresponding ones in substituted thiophenes. The IR carbonyl stretching frequencies in methyl (5-substituted 2-thiophenecarboxylate)s were correlated reasonably well with the chemical shifts of 5-protons in 2-substituted thiophenes. The coupling constants in methyl 2-thiophenecarboxylate series were found to very linearly with the electronegativities of the substituents.