Salicylhydrazone ligands for enantioselective addition of diethylzinc to aldehydes

A family of chiral salicylhydrazones was designed and synthesized for application in asymmetric catalysis. The ability of newly prepared binaphthyl-containing salicylhydrazones as the chiral ligand was examined in the addition of diethylzinc to aldehyde, with the desired product obtained in up to 80% ee.

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2-((E)-((R)-6,7-Dihydro-5H-dinaphtho[2,1-c;1′,2′-e]azepin-6-ylimino)methyl)phenolC29H22N2O[α]D21 = +357.1 (c 0.38, CHCl3)Source of chirality: 2,2′-binaphthol

2-tert-Butyl-6-((E)-((R)-6,7-dihydro-5H-dinaphtho[2,1-c;1′,2′-e]azepin-6-ylimino)methyl)phenolC33H30N2O[α]D25 = +367.7 (c 0.58, CHCl3)Source of chirality: 2,2′-binaphthol

4-tert-Butyl-2-((E)-((R)-6,7-dihydro-5H-dinaphtho[2,1-c;1′,2′-e]azepin-6-ylimino)methyl)phenolC33H30N2O[α]D25 = +321.7 (c 0.80, CHCl3)Source of chirality: 2,2′-binaphthol

4-Bromo-2-((E)-((R)-6,7-dihydro-5H-dinaphtho[2,1-c;1′,2′-e]azepin-6-ylimino)methyl)phenolC29H21BrN2O[α]D25 = +399.6 (c 0.20, CHCl3)Source of chirality: 2,2′-binaphthol

(R)-3,3′-Diformyl-2,2′-binaphthol bis-N-(dimethylamino)imineC26H26N4O2[α]D21 = −116.7 (c 0.28, CHCl3)Source of chirality: 2,2′-binaphthol

(R)-3,3′-Diformyl-2,2′-binaphthol bis-N-(pyrrolidinyl)imineC30H30N4O2[α]D21 = −128.1 (c 0.13, CHCl3)Source of chirality: 2,2′-binaphthol