Coupling of nonequivalent aromatic rings by soluble nickel catalysts. A general route to the 1,8-diarylnaphthalenes

Abstract

A facile route to the l,&diarylnaphthalene derivatives is described. The parent compound, l,8-diphenylnaphthalene, can be prepared in two steps with 35% overall yield from the commercial 1,8-diaminonaphthalene. The key step in these preparations is the direct joining of two nonequivalent aromatic molecules by an organonickel-catalyzed Grignard-aryl halide coupling reaction at -15 oC. The coupling reaction is regiospecific with respect to the position of substitution of both aromatic halves. The yields of thjs coupling reaction are high, even though the 1,8-diarylnaphthalenes are sterically crowded. The efficiency of the reaction under a variety of conditions is evaluated. The order of reactivity of aryl halides is found to be I > Br > Cl, and it is possible to effect coupling preferentially at an iodo group in the presence of a chloro group, the latter being available for further synthetic functionalization.