Catalytic Enantioselective Formation of C−C Bonds by Addition to Imines and Hydrazones: A Ten-Year Update

The use of chiral nonracemic onium salts and crown ethers as effective phase-transfer catalysts have been studied intensively primarily for enantioselective carbon-carbon or carbon-heteroatom bond-forming reactions under mild biphasic conditions. An essential issue for optimal asymmetric catalysis is the rational design of catalysts for targeted reaction, which allows generation of a well-defined chiral ion pair that reacts with electrophiles in a highly efficient and stereoselective manner. This concept, together with the synthetic versatility of phase-transfer catalysis, provides a reliable and general strategy for the practical asymmetric synthesis of highly valuable organic compounds.

Recent advances in asymmetric phase-transfer catalysis.

Recent development and application of chiral phase-transfer catalysts.

Catalytic Asymmetric Synthesis of α-Amino Acids

The asymmetric Mannich reaction ranks among the most potent enantioselective and diastereoselective C–C-bond forming reactions. In recent years, organocatalysed versions of asymmetric Mannich processes have been increasingly reported and used in a rapidly growing number of applications. This tutorial review provides an overview of the recent history of the asymmetric organocatalysed Mannich reaction, including scope and limitations, and application of different catalyst systems.

Organocatalysed asymmetric Mannich reactions.

Catalytic asymmetric synthesis of a nitrogen analogue of dialkyl tartrate by direct mannich reaction under phase-transfer conditions.

Phase-transfer-catalyzed direct Mannich reaction of glycinate Schiff base 3 with α-imino ester 4 has been accomplished with high enantioselectivity by the utilization of N-spiro C2-symmetric chiral quaternary ammonium bromide 2 as a catalyst. This methodology enables the catalytic asymmetric synthesis of differentially protected 3-aminoaspartate, a nitrogen analogue of dialkyl tartrate. The product (syn-5) was converted into a precursor (6) of streptolidine lactam.

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Jun-ichi Fujii

Papers

Catalytic asymmetric synthesis of a nitrogen analogue of dialkyl tartrate by direct mannich reaction under phase-transfer conditions.

Catalytic Asymmetric Synthesis of a Nitrogen Analogue of Dialkyl Tartrate by Direct Mannich Reaction under Phase-Transfer Conditions.