SYNTHESIS OF N-ALKYLATED AND N-ARYLATED DERIVATIVES OF 2-AMINO-2'-HYDROXY-1,1'-BINAPHTHYL (NOBIN) AND 2,2'-DIAMINO-1,1'-BINAPHTHYL AND THEIR APPLICATION IN THE ENANTIOSELECTIVE ADDITION OF DIETHYLZINC TO AROMATIC-ALDEHYDES

High-yield reductive alkylation of(R)-(+)-1 and (R)-(+)-2 has been acc omplished with a series of ketones (even as bulky as 2-adamantanone) a nd NaBH4/H2SO4 in THF at room temperature to give the respective N-alk ylated binaphthyls 6a-c, 9a-c, and 10a-c. Related N-phenyl derivatives 14, 16, and 17 were obtained via the Pd(O)-catalyzed coupling of(R)-( +)-1 and (R)-(+)-2, respectively, with PhBr; no racemization was obser ved. Subsequent reductive methylation with CH2O and NaBH4/H2SO4 afford ed the bidentate ligands 8a-c, 12a-c, 13a-c, 15, 18, and 19, which com prise a new class of binaphthyls. Their utility as chiral ligands has been demonstrated for the addition of Et2Zn to benzaldehyde and its co ngeners; the highest level of asymmetric induction was observed for N, N-dimethyl NOBIN (R)-(+)-3 (3 mol %) in conjunction with n-BuLi (5.4 m ol %), which gave (R)-(+)-21a in 88% ee. Derivatives of the amino phen ol 1 (NOBIN) proved more efficient than the corresponding diamines der ived from 2. The stereochemical outcome and the enhancement of asymmet ric induction by Li+ are discussed in terms of the chelated transition state 26.