A Facile Synthesis of the Enantiopure, Nitrogen-Substituted 2,2'-Diamino-1,1'-binaphthyls as Potential Ligands for Catalytic Asymmetric Reactions

Reductive alkylation of (R)-(+)-2,2'-diamino-1,1'-binaphthyl (1) with various ketones has been accomplished by means of NaBH4/H2SO4 in THF at room temperature. Bisalkylation predominated with the sterically less demanding acetone (1→3a; 82%), whereas the bulky 2-adamantanone afforded mainly the monoalkylated product 4c (71%). Both mono- and bisalkylated diamines (R)-3 and (R)-4 were reductively permethylated on reaction with CH2O, NaBH4, and H2SO4. The Pd(0)-catalyzed phenylation of (R)-(+)-1 with PhBr afforded the N,N'-diphenyl derivative (R)-7 (70%).