Tandem cross-Rauhut-Currier/cyclization reactions of activated alkenes to give densely functionalized 3,4-dihydropyrans

A novel tandem cross-Rauhut-Currier/cyclization reaction between α,β-unsaturated ketones was developed. Using DABCO (20 mol %) as the catalyst, a series of densely functionalized 3,4-dihydropyrans were obtained in excellent yields and stereoselectivities (up to 98% yield, >99:1 dr). A tentative catalytic cycle was proposed with key intermediates confirmed by ESIMS studies.