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 accomplished with a series of ketones (even as bulky as 2-adamantanone) and NaBH 4 /H 2 SO 4 in THF at room temperature to give the respective N-alkylated binaphthyls 6a − c, 9a − c, and 10a − c . Related N -phenyl derivatives 14, 16, and 17 were obtained via the Pd(0)-catalyzed coupling of ( R )-(+)- 1 and ( R )-(+)- 2, respectively, with PhBr; no racemization was observed. Subsequent reductive methylation with CH 2 O and NaBH 4 /H 2 SO 4 afforded the bidentate ligands 8a − c, 12a − c, 13a − c, 15, 18, and 19, which comprise a new class of binaphthyls. Their utility as chiral ligands has been demonstrated for the addition of Et 2 Zn to benzaldehyde and its congeners; the highest level of asymmetric induction was observed for N,N -dimethyl NOBIN ( R )-(+)- 3 (3 mol %) in conjunction with n -BuLi (5.4 mol %), which gave ( R )-(+)- 21a in 88% ee. Derivatives of the amino phenol 1 (NOBIN) proved more efficient than the corresponding diamines derived from 2 . The stereochemical outcome and the enhancement of asymmetric induction by Li + are discussed in terms of the chelated transition state 26 .