A chiral ammonium betaine, an intramolecular ion-pairing quaternary ammonium aryloxide 3, has been designed and its vast potential as an enantioselective organic base catalyst has been successfully demonstrated in the highly enantioselective direct Mannich-type reaction of alpha-substituted alpha-nitrocarboxylates 2 with various N-Boc imines 1. The present study provides a conceptually new approach toward the design of bifunctional, chiral quaternary ammonium salts and their utilizations as a homogeneous organic molecular catalyst.

Catalyst debut: The chiral ammonium betaine 1 has been successfully applied to the asymmetric Steglich rearrangement as an ionic nucleophilic catalyst. The catalyzed reaction results in record levels of product enantioselectivity, and has a broad substrate scope. M.S.=molecular sieves, Troc=2,2,2‐trichloroethoxycarbonyl.

A C(1)-symmetric chiral ammonium betaine has been developed, and its intramolecular ion-pairing structure in solid state and its catalytic performance to achieve the highly stereoselective Mannich-type reaction of 2-alkoxythiazol-5(4H)-ones are revealed.

No abstract

A new strategy for developing stereoselective bond-forming reactions is introduced; it takes advantage of the ionic nucleophilic catalysis of chiral ammonium betaines to utilize vinylic esters simultaneously as the enolate precursor and the acylating agent for coupling with electrophiles. Its synthetic utility is clearly demonstrated by the realization of a highly diastereo- and enantioselective aldol reaction from oxindole-derived vinylic carbonates.