Catalytic asymmetric intermolecular carbonyl–ene-type reactions of unactivated aldehydes and alkenes

Carbonyl–ene-type reactions are recognized by chemists for their ability to form carbon–carbon bonds between aldehydes and alkenes, both abundantly available early-stage chemicals. However, despite remarkable progress with intramolecular variants, intermolecular carbonyl–ene-type reactions in which unactivated aldehydes react with unactivated alkenes are underexplored and, to the best of our knowledge, catalytic enantioselective versions have not yet been described. Here we report a solution to this problem that enables a variety of unactivated aromatic and aliphatic aldehydes to be united with alkenes, furnishing highly enantioenriched homoallylic alcohols. The method benefits from the high reactivity of confined silylium ion-based organic Lewis acid catalysts, which, according to computational studies, mediate a cationic Prins-type pathway.