Thermally induced rearrangement of thiopheniobis(alkoxycarbonyl)methanides

Abstract

Thiopheniobis(alkoxycarbonyl)methanides undergo intramolecular rearrangement when heated, to give 2H-thiopyrans as thermally unstable kinetic products. When the methanides are subjected to prolonged heating thiophene-2-malonates are produced as the major rearrangement products. A mechanism for these transformations is advanced in an attempt to rationalise the known reactivity of thiophene and its derivatives towards diazoalkanes.