Regio- and Diastereodivergent [4+2] Cycloadditions with Cyclic 2,4-Dienones

By employing activated alkenes with bulky a functional groups, such as alpha-cyano-alpha,beta-unsaturated ketones and Meldrum's acid-based alkenes, a previously unreported cross-trienamine pathway of cyclic 2,4-dienones is adopted to deliver gamma',delta-regioselective [4 + 2] cycloadducts catalyzed by cinchona -derived amines. In addition, a diastereodivergent [4 + 2] cycloaddition reaction is realized with Z-configured 4-alkylideneisoxazol-5(4H)-ones under similar catalytic conditions, even through a three- or four-component cascade process with simple starting materials.