Thermally induced rearrangement of thiopheniobis(alkoxycarbonyl)methanides. A theoretical MNDO SCF-MO study

Abstract

The thermal rearrangements of thiopheniobis(hydroxycarbonyl)methanides to give inter alia 2H-thiopyrans, 2- and 3-substituted thiophenes, and 2,3-cyclopropanated thiophenes have been investigated theoretically using the MNDO SCF-MO method. These calculations indicate that a [1,2]-shift of the bis(hydroxycarbonyl)methanide group from the sulphur to an adjacent carbon atom can occur to form a dipolar intermediate (3). This intermediate is predicted to be the common precursor to all the products observed experimentally in this reaction. In addition, several novel products resulting from the rearrangement of (3) are predicted to be of sufficiently low energy to be capable of detection.