Substituent effects in ring-chain tautomerism of the condensation products of non-racemic 1,2-aminoalcohols with aromatic aldehydes

The condensation of (S)-2-amino-2-phenylethanol or (S)-2-amino-3-phenylpropanol with substituted benzaldehydes in methanol or water led to crystalline products, which proved to exist in CDCl3 at 300 K as three-component (ringcis-open-ringtrans) tautomeric mixtures. The electronic effects of the 2-aryl substituents on the tautomeric equilibria were described by the Hammett equation. Good correlations were found between the equilibrium constants and the Hammett–Brown parameter (σ+) of the substituent X on the 2-phenyl group.

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(S)-2-(4-Nitrobenzylideneamino)-2-phenylethanolC15H14N2O3[α]D25=-55.3 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Cyanobenzylideneamino)-2-phenylethanolC16H14N2O[α]D25=-60.0 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Bromobenzylideneamino)-2-phenylethanolC15H14BrNO[α]D25=-56.7 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Chlorobenzylideneamino)-2-phenylethanolC15H14ClNO[α]D25=-49.8 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-Benzylideneamino-2-phenylethanolC15H15NO[α]D25=-64.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Fluorobenzylideneamino)-2-phenylethanolC15H14FNO[α]D25=-39.1 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Methylbenzylideneamino)-2-phenylethanolC16H17NO[α]D25=-62.0 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Methoxybenzylideneamino)-2-phenylethanolC16H17NO2[α]D25=-81.4 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Dimethylaminobenzylideneamino)-2-phenylethanolC17H20N2O[α]D25=-154.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-2-phenylethanolAbsolute configuration: (S)

(S)-2-(4-Nitrobenzylideneamino)-3-phenylpropanolC16H16N2O3[α]D25=-247.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Cyanobenzylideneamino)-3-phenylpropanolC17H16N2O[α]D25=-280.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Bromobenzylideneamino)-3-phenylpropanolC16H16BrNO[α]D25=-240.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Chlorobenzylideneamino)-3-phenylpropanolC16H16ClNO[α]D25=-247.3 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-Benzylideneamino-3-phenylpropanolC16H17NO[α]D25=-247.5 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Fluorobenzylideneamino)-3-phenylpropanolC16H16FNO[α]D25=-222.7 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Methylbenzylideneamino)-3-phenylpropanolC17H19NO[α]D25=-267.2 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Methoxybenzylideneamino)-3-phenylpropanolC17H19NO2[α]D25=-276.9 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)

(S)-2-(4-Dimethylaminobenzylideneamino)-3-phenylpropanolC18H22N2O[α]D25=-399.0 (c 0.5, MeOH)Source of chirality: (S)-2-amino-3-phenylpropanolAbsolute configuration: (S)