We recently reported that the reaction of 1 with furans led to carbon-oxygen bond activation and ring-expansion (Figure ). The selectivity of this reaction could be controlled through addition of a palladium-catalyst and the scope expanded to include dihydrofurans and dihydropyrans. Under the same catalytic conditions, thiophene failed to undergo dearomatisation and ring-opening with 1, instead metalation at the 2-position was observed (Figure ). 32 Reaction of 1 with 1.1 equiv. of thiophene in C6D6 at 60 °C led to a mixture of hydrocarbon soluble products as identified by 1 H NMR spectroscopy which formed alongside a colourless crystalline precipitate (Scheme 1). Through variation of the reaction time, the stoichiometry and development of work-up procedures to partially separate mixtures, 2a, 3 and 4 were identified as the hydrocarbon soluble products of this reaction. These results contrast the reaction of 1 with thiophene in the presence of catalytic [Pd(PCy3)2] where C-H activation of the 2-position was observed as a major pathway. The insoluble side product was confirmed as the aluminium disulfide complex 5 through isolation and comparison of unit cell data obtained by X-ray diffraction to that in the literature. Compound 2a is characterised by resonance in the 1 H NMR spectrum at  = 4.87 (s, 1H) corresponding to the -diketiminate backbone methine. Analogues of 2a can be obtained on reaction of 1 with substituted thiophenes (vide infra).