Synthesis of new dimeric-PEG-supported cinchona ammonium salts as chiral phase transfer catalysts for the alkylation of Schiff bases with water as the solvent

The water-soluble PEG-supported cinchona ammonium salts were successfully synthesized and used as chiral phase transfer catalysts for the asymmetric alkylation of tert-butyl benzophenone Schiff base derivatives with high chemical yields (up to 98%) and enantioselectivities (up to 97%) in aqueous media. The recycling results showed that the polymers were stable and rarely lost activities.

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Diacetamido-PEG2000 N-bound cinchonidinium chloride[α]D20=-15.6 (c 0.4, CH2Cl2)

Diacetamido-PEG2000 N-bound quininium chloride[α]D20=-20.2 (c 0.4, CH2Cl2)

Diacetamido-PEG2000 N-bound cinchonium chloride[α]D20=+45.3 (c 0.4, CH2Cl2)

(S)-tert-Butyl-3-phenyl-2-diphenylmethylene amino propanoateC26H27NO2Ee = 83%[α]D20=-12.6 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(2-methylphenyl)-2-diphenylmethylene amino propanoateC27H29NO2Ee = 82%[α]D20=-14.1 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(3-methylphenyl)-2-diphenylmethylene amino propanoateC27H29NO2Ee = 90%[α]D20=-13.7 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(4-methylphenyl)-2-diphenylmethylene amino propanoateC27H29NO2Ee = 85%[α]D20=-15.7 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(2-chlorophenyl)-2-diphenylmethylene amino propanoateC26H26ClNO2Ee = 97%[α]D20=-16.3 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(3-chlorophenyl)-2-diphenylmethylene amino propanoateC26H26ClNO2Ee = 92%[α]D20=-16.6 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(4-chlorophenyl)-2-diphenylmethylene amino propanoateC26H26ClNO2Ee = 91%[α]D20=-15.8 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-(2-allyl)-2-diphenylmethylene amino propanoateC21H23NO2Ee = 86%[α]D20=-11.4 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-ethyl-2-diphenylmethylene amino propanoateC21H25NO2Ee = 90%[α]D20=-12.2 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

(S)-tert-Butyl-3-methyl-2-diphenylmethylene amino propanoateC20H23NO2Ee = 83%[α]D20=-10.8 (c 0.2, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S