Axially chiral quaternary ammonium

Axially Chiral Quaternary Ammonium Salt-Catalyzed Aldol Reactions... 

Quaternary ammonium betaines possessing an anion moiety have emerged as Bronsted base catalysts. The C2-symmetric axially chiral ammonium betaine 177 deprotonates the a-substituted a-nitrocarboxylates (176) to form a structured ion pair that reacts with imines (173) to furnish the corresponding anti-Mannich... 

Inspired by Maruoka s success in using axially chiral C2-symmetric binaphthyl-based N-spiro quaternary ammonium salts, both the Arai [83] and Waser [84] groups developed tartaric acid-derived N-spiro quaternary ammonium salts 51 and 52, respectively. These catalysts could promote the asymmetric alkylation and conjugate addition with good enantioselectivities. 

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