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research article
Highly enantioselective inverse-electron-demand hetero-Diels-Alder reactions of α,β-unsaturated aldehydes
Simple, α,β-unsaturated aldehydes are excellent substrates in the hetero-Diels-Alder reaction with inverse electron demand, catalyzed by the Cr(III)-Schiff base complex I in the presence of 4-Ǻ molecular sieves and without solvent. The resulting dihydropyrans are obtained with high enantio- (89-98% ee) and diastereoselectivity (> 95% de) and in good yields (40-95%).