Quantification of the Nucleophilicities of 3-X-Thiophenes: Highlighting the Hyperortho Correlation

Abstract

Kinetics studies for the coupling reactions of the 3-X-thiophene 1a-c (X = CH3, H and Br) with the electrophiles 2a and 3a-c have been investigated in acetonitrile at 20°C The second-order rate constants have been employed to determine the nucleophilicity parameters N and s of the thiophene 1 according the Mayr equation log k (20°C) = s (E + N). The nucleophilic-specific parameters N and s quantified in this work have been derived and compared with the reactivity of other C nucleophiles. Based on the linear correlations log k1 = f(E) and log k1 = f(σp+), we have shown that the mechanism of interactions occurs by a unique process: electrophilic heteroaromatic substitution of an α-carbon position of substituted 3-X-thiophenes 1 known hyperortho correlation.