Elimination Reactions of Aryl Furylacetates Promoted by R₂NH in MeCN: Effects of Base Solvent and β‐Aryl Group on the Ketene‐forming Transition State

Abstract

Ketene‐forming elimination from C4H3(O)CH2C(O)OC6H3‐2‐X‐4‐NO2 (1) promoted by R2NH in MeCN has been studied. The reactions produced elimination products and exhibited second‐order kinetics with Brönsted β = 0.51, and |βlg| = 0.47–0.53, indicating that the reaction proceeds by the E2 mechanism via an E2‐central transition state. Comparison of β, |βlg|, ΔH≠, and ΔS≠ values for R2NH‐promoted eliminations from ArCH2C(O)OC6H3‐2‐X‐4‐NO2 reveals that the transition‐state structures for Ar = furyl and thienyl are similar and more symmetrical than that for Ar = Ph. This outcome has been attributed to the greater double bond stabilizing ability of the former than that of the latter.