Synthesis of sterically controlled chiral β-amino alcohols and their application to the catalytic asymmetric sulfoxidation of sulfides

Sterically hindered and enantiomerically pure β-amino alcohols 8a and 8b were prepared from the enantiomerically pure aziridine-2-carboxylic acid menthol ester 13. Vanadium complexes of the chiral Schiff-base ligands prepared from the β-amino alcohols catalyze an efficient enantioselective sulfoxidation of alkyl aryl sulfides, while enantioselectivities as high as 96% ee can be observed in the sulfoxidation of benzyl aryl sulfides.

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(2R)-2-Amino-3-ethyl-3-methoxypentan-1-olC8H19NO2[α]D = +17.8 (c 0.1, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: R

(2S)-2-Amino-3-isobutyl-3-methoxy-5-methylhexan-1-olC12H27NO2[α]D = −10.0 (c 2.0, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: S

2,2-Dimethylpropionic acid (R)-3′-[(2R)-(2-ethyl-1-hydroxymethyl-2-methoxybutylimino)methyl]-2′-hydroxy[1,1′]binaphthalenyl-2-yl esterC34H39NO5[α]D = −36.0 (c 0.5, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: R,R

2,2-Dimethylpropionic acid (R)-2′-hydroxy-3′-[(1S,2R)-(2-hydroxyindan-1-ylimino)methyl]-[1,1′]binaphthalenyl-2-yl esterC35H31NO4[α]D = +53.2 (c 0.5, CHCl3)Source of chirality: indanol and BINOL (commercially available)Absolute configuration: R,S,R