[6+2] Cycloaddition of N-phenyltriazolinedione with cycloheptatriene derivatives mediated and stereodirected by a chiral 3-oxy substituent

The addition of N-phenyltriazolinedione to a 7,7-dimethylcycloheptatriene derivative afforded a [6+2] adduct, which was found to be produced by the rearrangement of an initially formed [4+2] adduct. The regioselectivity of the initial addition was controlled by the 3-oxy-substituent, which also mediates the PTAD addition to the tropilidene form. The chiral 3-substituent also controlled the stereoselectivity of the addition to a high degree.