A new kind of complex prepared from scandium(III) triflate and
L-proline-derived
N,
N'-dioxides hasbeen developed to catalyze the enantioselective aza-Diels-Alder reaction between 1,3-butadiene (diene
1) and aldimines
2, affording the corresponding 2,5-disubstituted dihydropyridinones in moderate to highyields (up to 92%) with good enantioselectivities (up to 90% ee) at room temperature. A variety ofaldimines including aromatic, heteroaromatic, conjugated, and aliphatic imines were found to be suitablesubstrates. Enantiopure samples (up to 99% ee) were obtained for some products by a singlerecrystallization. The absolute configuration of the products was determined by X-ray diffraction andCD analysis. On the basis of the investigation of
1H NMR spectra and the positive nonlinear effect, thecatalyst structure was carefully discussed.
