Synthesis of C2-symmetrical diamine based on (1R)-(+)-camphor and application to oxidative aryl coupling of naphthols

The new C-2-symmetrical 1,2-diamine {N,N'-bis[(1R,2R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-1,2-ethanedianiine)3 has been synthesized from commercial (1R)-(+)-camphor 1 and scrutinized as ligand in the oxidative biaryl coupling of naphthol derivatives. Under the optimal conditions employing a Cu(I)-3 triflate complex (10 mol%) in dichloroethane-MeCN and molecular sieves with air as the oxidant, aryl coupling of naphthol derivatives could be achieved in satisfactory yields (48-90% yield) and ees of up to 65%. The ester moiety at the 3-position of the substrate was found to be crucial for a satisfactory asymmetric induction in the present coupling reaction.