A powerful synergistic effect for highly efficient diastereo- and enantioselective phase-transfer catalyzed conjugate additions

An efficient, catalytic, diastereo- and enantioselective conjugate addition of N-(diphenylmethylene)glycine tert-butyl ester to beta-aryl substituted enones was realized in the presence of 1 mol% of newly desired dinuclear N-spiro-ammonium salts, affording functionalized alpha-amino acid derivatives in 57-98% yields with high diastereoselectivity (up to 99 : 1 dr) and enantioselectivity (up to 96.5 : 3.5 er).