Phase-transfer catalysis Mannich reactions

Michael-aldol reaction as an alternative to the Morita-Baylis-Hillman reaction 14 recent results in conjugate addition of nitroalkanes to electron-poor alkenes 15 asymmetric cyclopropanation of chiral (l-phosphoryl)vinyl sulfoxides 16 synthetic methodology using tertiary phosphines as nucleophilic catalysts in combination with allenoates or 2-alkynoates 17 recent advances in the transition metal-catalysed asymmetric hydrosilylation of ketones, imines, and electrophilic C=C bonds 18 Michael additions catalysed by transition metals and lanthanide species 19 recent progress in asymmetric organocatalysis, including the aldol reaction, Mannich reaction, Michael addition, cycloadditions, allylation, epoxidation, and phase-transfer catalysis 20 and nucleophilic phosphine organocatalysis.21... 

The versatile nature of cinchona alkaloid ammonium salts for phase-transfer catalysis can be illustrated by recent reports on conjugate additions [118] and a nitro-Mannich reachon [119]. Dimeric catalysts derived from quinine and quini-dine were applied in the conjugate addition of cyclic (l-ketoesters to a, 3-unsaturated carbonyl compounds. The reaction proceeded in the presence of a tertiary amine as base and afforded the products in moderate to high yield and enantioselectivity (Scheme 6.56). 

The asymmetric synthesis of nemonapride 92 was achieved by applying the Mannich-type reaction of the Schiff base 1 with A-Boc aliphatic imine 93 under the phase-transfer catalysis of (S,S)-TaDiAS (PTC 11) (Scheme 4.22)." The differently protected a,(3-diamino acid ester 94 was isolated in 72% yield with 65% ee, which was then transformed into the stereochemicaUy pure pyrrolidine derivative 95, an important precursor of the target 92. 

Abstract The organocatalytic asymmetric Mannich reaction and the related aza-Morita-Baylis-Hillman have been reviewed. The activities in this field have been snbdivided based on the types of catalysts that have been ntilized, which includes catalysis by enamine-forming chiral amines, chiral Br0nsted bases, chiral Brpnsted acids, and phase-transfer catalysts. 

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