Asymmetric Henry reaction catalyzed by Cu(II)-based chiral amino alcohol complexes with C2-symmetry

A series of chiral amino alcohol ligands was prepared using commercial amino alcohols and phthalaldehydes. These ligands were used as catalysts in asymmetric Henry reactions in the presence of Cu(II) ions giving good yields (up to 97%) and enantiomeric excesses (ee, up to 98%). The DFT calculations showed the effect of the trans/cis configurations of the Cu-complexes on the origin of enantioselectivity. The easy catalyst preparation, mild reaction conditions, high yields and excellent enantioselectivities make these catalysts suitable for widespread use.

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(S)-(−)-2-Benzylamino-3-phenylpropan-1-olC16H19NO[α]D25 = −23.8 (c 1.06, CH2Cl2)Absolute configuration: (S)

(S)-(−)-2-Phenylamino-2-phenylethan-1-olC15H17NO[α]D25 = −26.2 (c 1.14, CH2Cl2)Absolute configuration: (S)

(−)-N,N′-Bis[(2S)-1-hydroxy-3-phenylpropan-2-yl]-1,4-xylylenediamineC26H32N2O2[α]D25 = −48.7 (c 1.44, CH2Cl2)Absolute configuration: (S)

(−)-N,N′-Bis[(1S)-2-hydroxy-1-phenylethyl]-1,4-xylylenediamineC24H28N2O2[α]D25 = −51.6 (c 1.38, CH2Cl2)Absolute configuration: (S)

(−)-N,N′-Bis[(2S)-1-hydroxy-3-phenylpropan-2-yl]-1,3-xylylenediamineC26H32N2O2[α]D25 = −44.2 (c 1.33, CH2Cl2)Absolute configuration: (S)