Abstract
The carbonyl-ene reaction between aldehydes and olefins constitutes a perfectly atom economic approach to homoallylic alcohols with concomitant C-C bond formation. However, the scope of catalytic asymmetric intermolecular versions is currently limited to activated substrates, while of the two intramolecular types only catalytic asymmetric (ene-exo)-carbonyl-ene type cyclizations can be considered mature. The corresponding (ene-endo)-cyclizations would arguably find equal utility in chemical synthesis but remain underdeveloped. Herein, we report an efficient regio- and enantioselective catalytic asymmetric (ene-endo)-carbonyl-ene type cyclization of unbiased alkenyl aldehydes using a strong and confined IDPi Brønsted acid catalyst. High enantioselectivities of up to 98:2 e.r. were obtained for a range of homoallylic alcohols.