Asymmetric borane reduction of prochiral ketones catalyzed by C3-symmetric sulfonamide

A novel, recoverable, C3-symmetric sulfonamide L-1 has been developed for the asymmetric borane reduction of prochiral ketones in refluxing THF. The optically active secondary alcohols were obtained in excellent enantiometric excesses (up to 97% ee) and good yields. The C3-symmetric sulfonamide L-1 can be easily recovered and reused four times without any significant loss of catalytic activity.

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(R)-1-Phenyl-ethanolC8H10O[α]D20=+38.2 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(4-Chlorophenyl)-ethanolC8H9ClO[α]D20=+45.8 (c 1.1, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(4-Methoxylphenyl)-ethanolC9H12O2[α]D20=+46.5 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(4-Nitrophenyl)-ethanolC8H9NO3[α]D20=+26.5 (c 1.5, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(4-Bromophenyl)-ethanolC8H9BrO[α]D20=+31.5 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(4-Fluorophenyl)-ethanolC8H9FO[α]D20=+34.5 (c 2.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(3-Bromophenyl)-ethanolC8H9BrO[α]D20=+37.5 (c 1.5, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(3-Methoxylphenyl)-ethanolC9H12O2[α]D20=+32.8 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(3-Methylphenyl)-ethanolC9H12O[α]D20=+45.8 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-(2-Fluorophenyl)-ethanolC8H9FO[α]D20=+34.1 (c 2.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(S)-2-Bromo-1-phenylethanolC8H9BrO[α]D20=+34.9 (c 1.7, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (S)

(S)-2-Chloro-1-(4-methoxyphenyl)-ethanolC9H11ClO2[α]D20=+32.5 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (S)

(S)-2-Bromo-1-(2,4-dimethylphenyl)-ethanolC10H13BrO[α]D20=+37.4 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (S)

(R)-1-(2-Naphthyl)-ethanolC12H12O[α]D20=+36.5 (c 2.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1,2,3,4-Tetrahydronaphthalen-1-olC10H12O[α]D20=-21.3 (c 1.5, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(R)-1-Phenyl-propanolC9H12O[α]D20=+24.6 (c 1.0, CH2Cl2)Source of chirality: chiral catalysisAbsolute configuration: (R)

(S)-[1-(4-{4-[1,1-Bis-(4-{4-[2-(hydroxy-diphenyl-methyl)-pyrrolidine-1-sulfonyl]-benzyloxy}-phenyl)-ethyl]-phenoxymethyl}-benzenesulfonyl)-pyrrolidin-2-yl]-diphenyl-methanolC97H87N3O12S3[α]D20=-54.8 (c 2.0, CH2Cl2)Source of chirality: l-prolineAbsolute configuration: (S)

(S)-(1-(4-(Phenoxymethyl)phenylsulfonyl)pyrrolidin-2-yl)diphenylmethanolC30H29NO4S[α]D20=-66.5 (c 2.0, CH2Cl2)Source of chirality: l-prolineAbsolute configuration: (S)