Asymmetric catalysis of carbon–carbon bond forming reactions using amino acid-derived C1-symmetrical salen ligands

Four amino acids (alanine, valine, phenylalanine and phenylglycine) have been converted into C1-symmetrical salen ligands and complexed to titanium, vanadium, copper and cobalt. The resulting complexes have been used as asymmetric catalysts for asymmetric cyanohydrin synthesis, asymmetric Strecker reactions, asymmetric synthesis of α-methyl amino acids and asymmetric Darzens condensations. Satisfactory levels of asymmetric induction were obtained from reactions in which the (salen)metal complex acts as a chiral Lewis acid, but low levels of asymmetric induction were obtained from reactions carried out under solid–liquid phase-transfer conditions.

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(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1,2-diaminopropaneC33H50N2O2[α]D20=+173.0 (c 0.1, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-phenyl-1,2-diaminopropaneC39H54N2O2[α]D20=+63.5 (c 0.052, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

(1R)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1-phenyl-1,2-diaminoethaneC38H53N2O2[α]D20=-27.2 (c 0.25, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-methyl-1,2-diaminobutaneC35H54N2O2[α]D20=+84.0 (c 0.1, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxy benzylidene)]-1,2-diaminopropaneC19H22N2O4[α]D20=+425.0 (c 0.04, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxy benzylidene)]-3-phenyl-1,2-diaminopropaneC25H26N2O4[α]D20=+67.0 (c 0.06, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

(1R)-[N,N′-Bis-(2′-hydroxy-4′-methoxy benzylidene)]-1-phenyl-1,2-diaminoethaneC24H24N2O4[α]D20=-60.0 (c 0.06, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxy benzylidene)]-3-methyl-1,2-diaminobutaneC21H26N2O4[α]D20=+78.6 (c 0.5, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1,2-diaminopropaneC17H18N2O2[α]D20=+332.0 (c 0.05, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-phenyl-1,2-diaminopropaneC23H22N2O2[α]D20=+88.0 (c 0.05, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-methyl-1,2-diaminobutaneC19H22N2O2[α]D20=+250.0 (c 0.03, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1,2-diaminopropanato] titaniumIV chlorideC33H48N2O2TiCl2[α]D20=+800.0 (c 0.003, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-phenyl-1,2-diaminopropanato] titaniumIV chlorideC39H52N2O2TiCl2[α]D20=-266.7 (c 0.006, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

[(1R)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1-phenyl-1,2-diaminoethanato] titaniumIV chlorideC38H50N2O2TiCl2[α]D20=+1300.0 (c 0.004, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-methyl-1,2-diaminobutanato] titaniumIV chlorideC35H52N2O2TiCl2[α]D20=-240.0 (c 0.005, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1,2-diaminopropanato] vanadiumV chlorideC33H48N2O3VCl[α]D20=+1050.0 (c 0.002, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-phenyl-1,2-diaminopropanato] vanadiumV chlorideC39H52N2O3VCl[α]D20=-690.0 (c 0.02, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

[(1R)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-1-phenyl-1,2-diaminoethanato] vanadiumV chlorideC38H50N2O3VCl[α]D20=+320.0 (c 0.02, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(2S)-[N,N′-Bis-(2′-hydroxy-3′,5′-di-tert-butyl benzylidene)]-3-methyl-1,2-diaminobutanato] vanadiumV chlorideC35H52N2O3VCl[α]D20=-3600.0 (c 0.0033, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1,2-diaminopropanato] copperIIC17H16N2O2Cu[α]D20=-140.0 (c 0.02, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-phenyl-1,2-diaminopropanato] copperIIC23H20N2O2Cu[α]D20=-320.0 (c 0.01, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

[(1)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1-phenyl-1,2-diaminoethanato] copperIIC22H18N2O2Cu[α]D20=-400.0 (c 0.01, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(1)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1-phenyl-1,2-diaminoethaneC22H20N2O2[α]D20=+88.0 (c 0.05, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-methyl-1,2-diaminobutanato] copperIIC19H22N2O2Cu[α]D20=-160.0 (c 0.01, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1,2-diaminopropanato] cobaltIIC17H16N2O2Co[α]D20=-1180.0 (c 0.02, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-phenyl-1,2-diaminopropanato] cobaltIIC23H20N2O2Co[α]D20=-720.0 (c 0.01, CHCl3).Prepared from (S)-phenylalanineAbsolute configuration: (2S)

[(1)-[N,N′-Bis-(2′-hydroxybenzylidene)]-1-phenyl-1,2-diaminoethanato] cobaltIIC22H18N2O2Co[α]D20=+640.0 (c 0.01, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(2S)-[N,N′-Bis-(2′-hydroxybenzylidene)]-3-methyl-1,2-diaminobutanato] cobaltIIC19H22N2O2Co[α]D20=-707.7 (c 0.013, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxybenzylidene)]-1,2-diaminopropanato] cobaltIIC19H20N2O4Co[α]D20=-560.0 (c 0.01, CHCl3)Prepared from (S)-alanineAbsolute configuration: (2S)

[(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxybenzylidene)]-3-phenyl-1,2-diaminopropanato] cobaltIIC25H24N2O4Co[α]D20=-1500.0 (c 0.02, CHCl3)Prepared from (S)-phenylalanineAbsolute configuration: (2S)

[(1R)-[N,N′-Bis-(2′-hydroxy-4′-methoxybenzylidene)]-1-phenyl-1,2-diaminoethanato] cobaltIIC24H22N2O4Co[α]D20=+440.0 (c 0.01, CHCl3)Prepared from (R)-phenylglycineAbsolute configuration: (1R)

[(2S)-[N,N′-Bis-(2′-hydroxy-4′-methoxybenzylidene)]-3-methyl-1,2-diaminobutanato] cobaltIIC19H24N2O4Co[α]D20=-160.0 (c 0.01, CHCl3)Prepared from (S)-valineAbsolute configuration: (2S)