The products of an imino Diels–Alder reaction with 2-trimethylsilyloxycyclohexadiene: synthesis, X-ray crystal structures, and mechanistic implications

The reaction of the N-tosyl imino-ester (1) with 2-trimethylsilyloxycyclohexadiene (2) followed by acidic work-up shows a divergence in pathways: at low temperature in polar solvents the cyclohexenones (5) and (6)(X-ray) are favoured, whereas at higher temperatures the bicyclic ketones (3) and (4)(X-ray) are the predominant products.