Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes

Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes have been studied with NMR techniques. Among them the complex with the Schiff base obtained from 2-hydroxy-3-isopropylbenzaldehyde, is the most selective catalyst for the cyanosilylation of aliphatic, alicyclic, aromatic, and heteroaromatic aldehydes. The highest enantioselectivity, >99%, was achieved for the addition of trimethylsilyl cyanide to cinnamaldehyde.

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(S)-2-Hydroxy-2-phenylacetonitrileC8H7NO[α]D20=-8.6 (c 0.50, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(S)-2-Hydroxy-2-(3-methoxyphenyl)acetonitrileC9H9NO2[α]D20=-10.2 (c 0.69, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-Hydroxy-2-(4-methoxyphenyl)acetonitrileC9H9NO2[α]D20=+23.9 (c 0.54, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S)-2-Hydroxy-2-(o-tolyl)acetonitrileC9H9NO[α]D20=-8.9 (c 0.46, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-Hydroxy-2-(m-tolyl)acetonitrileC9H9NO[α]D20=+8.9 (c 0.54, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(R)-2-Hydroxy-2-(p-tolyl)acetonitrileC9H9NO[α]D20=+11.5 (c 0.60, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S)-2-(2-Chlorophenyl)-2-hydroxyacetonitrileC8H6ClNO[α]D20=-1.0 (c 0.98, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-(3-Chlorophenyl)-2-hydroxyacetonitrileC8H6ClNO[α]D20=+15.5 (c 0.51, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(R)-2-(4-Chlorophenyl)-2-hydroxyacetonitrileC8H6ClNO[α]D20=+14.8 (c 0.79, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S)-2-(2-Bromophenyl)-2-hydroxyacetonitrileC8H6BrNO[α]D20=-1.2 (c 0.98, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-(4-Bromophenyl)-2-hydroxyacetonitrileC8H6BrNO[α]D20=+1.7 (c 0.92, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S)-2-(4-Fluorophenyl)-2-hydroxyacetonitrileC8H6FNO[α]D20=-16.2 (c 0.79, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(S)-2-Hydroxy-2-(3-nitrophenyl)acetonitrileC8H6N2O3[α]D20=-15.2 (c 0.95, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(S)-2-Hydroxy-2-(naphthalen-1-yl)acetonitrileC12H9NO[α]D20=-60.1 (c 0.89, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-Hydroxy-2-(naphthalen-2-yl)acetonitrileC12H9NO[α]D20=+18.1 (c 0.67, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S)-2-(Furan-2-yl)-2-hydroxyacetonitrileC6H5NO2[α]D20=-14.7 (c 0.35, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(R)-2-Cyclopentyl-2-hydroxyacetonitrileC7H11NO[α]D20=+3.1 (c 0.47, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(R)-2-Cyclohexyl-2-hydroxyacetonitrileC8H13NO[α]D20=+2.3 (c 0.56, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (R)

(S,E)-2-Hydroxy-4-phenylbut-3-enenitrileC10H9NO[α]D20=-21.8 (c 0.97, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S,E)

(S)-2-HydroxypentanenitrileC5H9NO[α]D20=-21.8 (c 0.97, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(S)-2-HydroxyheptanenitrileC7H13NO[α]D20=-17.8 (c 0.77, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(S)-2-HydroxyundecanenitrileC11H21NO[α]D20=-3.4 (c 0.61, CHCl3)Source of chirality: asymmetric addition of CN−Absolute configuration: (S)

(1R,2S,4S)-3-((E)-(2-Hydroxybenzylidene)amino)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olC17H23NO2[α]D20=+104.6 (c 0.182, CHCl3)Source of chirality: the precursorAbsolute configuration: (1R,2S,4S), 3-(E)

(1R,2S,4S)-3-((E)-(2-Hydroxy-3-methylbenzylidene)amino)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olC18H25NO2[α]D20=+95.4 (c 0.268, MeOH)Source of chirality: the precursorAbsolute configuration: (1R,2S,4S), 3-(E)

(1R,2S,4S)-3-((E)-(2-Hydroxy-3-isopropylbenzylidene)amino)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olC20H29NO2[α]D20=+87.4 (c 0.270, MeOH)Source of chirality: the precursorAbsolute configuration: (1R,2S,4S), 3-(E)

(1R,2S,4S)-3-((E)-(3,5-Di-tert-butyl-2-hydroxybenzylidene)amino)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olC25H39NO2[α]D20=+68.2 (c 0.290, MeOH)Source of chirality: the precursorAbsolute configuration: (1R,2S,4S), 3-(E)

(1R,2S,4S)-3-((E)-(4-(Diethylamino)-2-hydroxybenzylidene)amino)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-olC21H32N2O2[α]D20=+57.4 (c 0.270, MeOH)Source of chirality: the precursorAbsolute configuration: (1R,2S,4S), 3-(E)