Amine-catalyzed direct self Diels–Alder reactions of α,β-unsaturated ketones in water: synthesis of pro-chiral cyclohexanones

Amine-catalyzed direct self Diels–Alder reactions of α,β-unsaturated ketones have been developed. (S)-1-(2-Pyrrolidinyl-methyl)pyrrolidine, l-proline and pyrrolidine catalyzed the reaction of α,β-unsaturated ketones to provide cyclohexanone derivatives with good yield (up to 80%) in a single step via in situ-generation of 2-amino-1,3-butadienes and iminium ion-activated enones. Pro-chiral cyclohexanones were selectively prepared with pyrrolidine catalysis in water.