2H-benzimidazoles (isobenzimidazoles). Part 3. Thermal isomerisation of substituted 2H-benzimidazoles to 1H-benzimidazoles
Abstract
2H-Benzimidazole-2-spirocyclohexanes (1) when heated undergo a 1,5-sigmatropic rearrangement to 2,3-disubstituted 1H-benzimidazoles. A decided effect on the direction of this Isomerisation was observed with substituents in the homodiene ring.