Asymmetric Phase-Transfer Catalyzed Conjugate Addition Reaction Of α-Aryl Esters

The 1,4-conjugate addition reaction of carbon nucleophiles with unsaturated olefins is one of the most mature and commonly used carbon-carbon bond-forming reactions in organic chemistry.In the field of asymmetric phase-transfer catalysis,significant progress has been made in the conjugate addition reactions of 1,3-dicarbonyl compounds,ketones,oxindoles and glycine schiff bases,but the conjugate addition reactions ofα-aryl esters with low-activity has always been a challenge.At present,only chiral crown ethers catalyzed the conjugate addition reaction ofα-aryl esters has been reported,but moderate enantioselectivities have been obtained.This thesis studied the chiral quaternary ammonium salts catalyzed asymmetric conjugate addition reaction ofα-aryl esters.In the first chapter,the research progress of phase-transfer catalyzed asymmetric conjugate addition reactions of carbonyl compounds was reviewed,including ketones,1,3-dicarbonyl compounds,oxindoles and glycine schiff bases whose pKa values ofα-H less than 20,while the conjugate addition reactions ofα-aryl esters whose pKa values ofα-H greater than 20 have not been successful.In the second chapter,we studied the asymmetric conjugate addition reaction ofα-aryl esters catalyzed by chiral quaternary ammonium salts.Through the screening of catalysts,bases,solvents and temperature conditions,the optimal reaction conditions were determined as follows:dibutylammonium salt 3c with 4-tert-butylphenyl as side chain as catalyst,CsOH·H₂O as base,methyl tert-butyl ether as solvent at-40℃.Under this standard condition,the target product with chiral quaternary carbon center can be obtained with 59%ee and 85%yield.The electrophiles in this reaction can beα,β-unsaturated esters andα,β-unsaturated amides,however,α,β-unsaturated aldehydes,ketones,nitriles and sulfones,cannot react.For nucleophiles,α-aryl esters with electron-donating and electron-withdrawing groups can react,butα-aryl acetamides and lactones were not compatible.This reaction provides a new strategy for the asymmetric conjugate addition reaction of carbonyl compounds with low activity.