Diels-Alder Reaction of Nitroolefins

Significance

The diastereoselective and enantio­selective formation of bicyclic Diels-Alder products 4 starting from α,β-unsaturated cyclic ketones 1 of different ring sizes and (hetero)aromatic nitroolefins 2 is described. Aliphatic nitroolefins give only traces of product. Commercially available, chiral diamine 3 in combination with DNBSA was used as catalyst. In accordance with the observed absolute stereochemistry, the reaction is suggested to proceed via a stepwise domino double Michael addition pathway. Alternatively, a concerted Diels-Alder mechanism may be considered.