Simple chiral derivatisation protocols for NMR analysis of the enantiopurity of 1,2-diphenylethane-1,2-diamine and N-Boc-cyclohexane-1,2-diamine

Practically simple three-component chiral derivatisation protocols for determining the enantiopurity of vicinal C2-symmetric diamines by 1H NMR spectroscopic analysis are described. This involves the treatment of 1,2-diphenylethane-1,2-diamine or N-Boc-cyclohexane-1,2-diamine with 2-formylphenylboronic acid and enantiopure BINOL, which afford mixtures of diastereoisomeric boronate esters whose ratio is an accurate reflection of the enantiopurity of the parent diamine.

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(4S,5S)-2-(2-((R)-Naphtho[2,1,9,14-def][1,3,2]dioxaborepin-4-yl)phenyl)-4,5-diphenylimidazolidineC41H31BN2O2[α]D20=-302 (c 1.2, CH2Cl2)Absolute configuration: (4S,5S,R)

(4R,5R)-2-(2-((R)-Naphtho[2,1,9,14-def][1,3,2]dioxaborepin-4-yl)phenyl)-4,5-diphenylimidazolidineC41H31BN2O2[α]D20=+314 (c 1.7, CH2Cl2)Absolute configuration: (4R,5R,R)

tert-Butyl (E,1R,2R)-2-((2-((S)-naphtho[15,10,1,2-def][1,3,2]dioxaborepin-4-yl)phenyl)methyleneamino)cyclohexylcarbamateC38H37BN2O4[α]D20=-429 (c 1.1, CH2Cl2)Absolute configuration: (1R,2R,S)

tert-Butyl (E,1S,2S)-2-((2-((S)-naphtho[15,10,1,2-def][1,3,2]dioxaborepin-4-yl)phenyl)methyleneamino)cyclohexylcarbamateC38H37BN2O4[α]D20=+414 (c 2.0, CH2Cl2)Absolute configuration: (1S,2S,S)