Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by Ti(IV) complexes of C2-symmetrical chiral BINOL derivatives

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Enantioselective addition of diethylzinc to a series of aromatic aldehydes is developed using new chiral C 2-symmetric ligand ( S)-2,2′-(1,1′-binaphthyl-2,2′-diylbis(oxy))bis(methylene)bis(4-nitrophenol) ( S)- 2b. The catalytic system employing 10 mol % of ( S)- 2b and 120 mol % of Ti(O iPr) 4 was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 89% ee and up to 95% yield of the corresponding secondary alcohol under mild conditions.