Aryliminodimagnesium reagents. XIX. Effects of miscellaneous metal halides on oxidative self-coupling of the reagent, and on its condensation with nitrobenzene. A new preparative route to o,o'-dihydroxyazobenzene.

Fourteen metal halides (MXn) were each added to the solutions of aryliminodimagnesium (p-RC6H4N(MgBr)2, IDMg) in tetrahydrofuran, and the effect of MXn on relative yields of products was examined in the following three IDMg reactions: (A) oxidative coupling leading to symmetrical azobenzene, (B) condensation with nitrobenzene, and (C) condensation with o-hydroxy-substituted (o-HO) nitrobenzene. Reaction A was promoted by addition of CuCl2, and the yield of azoxybenzenes in reaction B was improved by addition of NiCl2 or CdCl2. Reaction C was similarly modified by addition of CdCl2 so as to improve the yield of o-HO-azoxybenzenes. Their acetyl derivatives underwent a facile photoinduced migration of azoxy oxygen and were successively hydrolyzed to afford bidentate chelating agents, o,o′-(HO)2-azobenzenes.

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