Ring-Expansion and Desulfurisation of Thiophenes with an Aluminium(I) Reagent

Reactions of thiophene, 2-methylthiophene, 2-methoxythiophene, 2,3-dimethylthiophene, and benzothiophene with the aluminium(I) complex [{(ArNCMe)2CH}Al] (Ar = 2,6-di-isopropylphenyl) are reported. In all cases, carbon–sulfur bond activation and ring-expansion of the heterocycle is observed. For thiophene, we identify a reaction network for desulfurisation that includes an unusual second carbon–sulfur bond activation step.