Diels-Alder Reaction of 2-Pyrones and α,β-Unsaturated Ketones

Significance

An effective method for the Diels-Alder reaction of simple α,β-unsaturated ketones with 2-pyrones is reported. For this transformation readily available cinchona alkaloid-derived catalysts 1a or 1b in combination with TFA were used. Various Diels-Alder adducts were obtained in high yields, diastereoselectivities and enantiomeric ratios. The reaction is highly chemoselective, furnishing predominantly the Diels-Alder rather than the Michael product. The reaction presumably proceeds via an iminium ion intermediate.