Asymmetric Henry reaction catalyzed by chiral secondary diamine-copper(II) complexes

The enantioselective Henry reaction was efficiently carried out under mild reaction conditions in 96% ethanol. The chiral C2-symmetric, secondary bisamines based on the 1,2-diaminocyclohexane framework and copper(II) acetate were found to promote the asymmetric nitroaldol reaction. Aromatic and aliphatic aldehydes were reacted with nitromethane to provide the corresponding β-nitroalcohols in very good yields and enantioselectivities up to 94%.

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(1R,2R)-N,N′-Bis((naphtalen-2-yl)methyl)cyclohexane-1,2-diamineC28H30N2[α]D=+15.9[α]D=+15.9 (c 0.4, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(2(octyloxy)benzyl)cyclohexane-1,2-diamineC38H58N2O2[α]D=-33.0[α]D=-33.0 (c 0.2, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(2chlorobenzyl)cyclohexane-1,2-diamineC20H24Cl2N2[α]D=-62[α]D=-62 (c 0.5, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(3-chlorobenzyl)cyclohexane-1,2-diamineC20H24Cl2N2[α]D=-53[α]D=-53 (c 0.5, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(4-bromobenzyl)-N,N′-dimethylcyclohexane-1,2-diamineC22H28Br2N2[α]D=+10.9[α]D=+10.9 (c 1.6, CH2Cl2)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(4-chlorobenzyl)cyclohexane-1,2-diamine copper(II) acetateC25H32Cl2CuN2O4[α]D=+475[α]D=+475 (c 0.016, CH2Cl2)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(4-chlorobenzyl)cyclohexane-1,2-diamineC20H24Cl2N2[α]D=-46.2[α]D=-46.2 (c 0.5, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(2,6-dichlorobenzyl)cyclohexane-1,2-diamineC20H22Cl4N2[α]D=-36.2[α]D=-36.2 (c 0.9, EtOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)

(1R,2R)-N,N′-Bis(2-bromobenzyl)cyclohexane-1,2-diamineC20H24Br2N2[α]D=-43.9[α]D=-43.9 (c 0.5, MeOH)Source of chirality: (1R,2R)-diaminocyclohexaneAbsolute configuration: (R,R)