Organocatalytic Enantioselective 1,8-Addition for the Synthesis of Chiral Tetraarylmethanes from 2-Naphthol/Naphthalen-2-amine-Based Tertiary Alcohols

Catalyticenantioselective construction of optically active tetraarylmethanesremains a challenging issue in the field of asymmetric synthesis becauseof the overwhelming steric hindrance and formidable stereocontrolthat existed in construction of the all-aryl-substituted quaternarycarbon stereocenter. Here, we reported an organocatalytic asymmetricsynthesis of chiral tetraarylmethanes from racemic tertiary alcohols.With the aid of a chiral phosphoric acid catalyst, 6-methylenenaphthalen-2(6H)-ones were generated in situ from 6-(hydroxydiarylmethyl)naphthalen-2-ols,followed by stereoselective 1,8-conjugate addition to afford the correspondingtetraarylmethanes in high to excellent yields with high enantioselectivities.Furthermore, the scope of tertiary alcohols has been successfullyenlarged to 6-(hydroxydiphenylmethyl)naphthalen-2-amines. Notably,it is the first time to use 2-naphthol/naphthalen-2-amine unit asthe auxiliary group to in situ generate & alpha;,& beta;,& gamma;,& delta;,& epsilon;,& zeta;-conjugatesystems, which have been successfully involved in organocatalyticremote stereocontrolled 1,8-conjugate addition reactions. Particularly,organocatalytic stereoconvergent formal nucleophilic substitutionreaction of triarylmethanols has been achieved for the asymmetricconstruction of chiral tetraarylmethanes. In addition, DFT calculationshave been applied to provide guidance for the design of additionaltertiary alcohols and understand the origin of stereoselectivity.