3‐Substituted thiophenes. XII. Bromination of β‐3‐thienylacrylic acid

Abstract

AbstractBromination of β‐3‐thienylacrylic acid in glacial acetic acid gave β‐(2‐bromo‐3‐thienyl)‐acrylic acid with an equivalent of bromine, and β‐(2,5‐dibromo‐3‐thienyl)‐α,β‐dibromo‐propionic acid with excess bromine. In hot carbon tetrachloride, an excellent yield of the stable olefinic addition product, β‐3‐thienyl‐α,β‐dibromopropionic acid, was obtained, and its structure was confirmed by conversion to β‐bromo‐3‐thienylethylene in base. 3‐Thenaldehyde underwent a Darzen's Glycidic Ester condensation to produce ethyl β‐3‐thienyl‐α,β‐epoxypropionate, but treatment of this ester or the salt of its derived acid with hydrogen bromide led to the formation of unstable products. The structure of the bromo‐acids and derivatives were confirmed by unequivocal syntheses and/or by nuclear magnetic resonance spectra.