ARYLIMINODIMAGNESIUM REAGENTS .25. COOPERATION OF ARYLIMINODIMAGNESIUM MOLECULES - DEOXYGENATION OF AZOXYARENES BY MONOFUNCTIONAL AND BIFUNCTIONAL REAGENTS IN COMPARISON WITH THAT BY PHOSPHORUS(III) REAGENTS

Reaction of aryliminodimagnesium [ArN(MgBr)(2), IDMg] with nitrobenzen e ((ArNO2)-N-1) in tetrahydrofuran (THF) gives unsymmetrical (unsym) a zoxybenzene, which is deoxygenated to give unsym-azobenzene. The react ion is utilized for the independent preparation of ONN and NNO isomers of unsym-azoxy compounds. The effects of the relative value of the di fference between oxidation and reduction potentials of para-substitute d reactants, special effects of ortho-substituents of the substrate an d also effects of structure and concentration of mono- and bis-IDMg re agents were studied previously, and 'cooperation of their aggregate ex cess needed for product formation' was proposed. This unfamiliar conce pt for reactions of magnesium reagents was studied further. Supporting evidence was obtained from the retarding effect of trimethylene chain s of nitro [3.3] metacyclophanes and the derived azoxy [3.3] metacyclo phanes and also from the effect of the length of bis-IDMg's central al pha,omega-polymethylenedioxy chain appropriate for azoxy deoxygenation . By comparison with deoxygenation by X(3)P reagents (X = EtO, Me(2)N) , the general needs of cooperation of excess magnesium reagents were c onfirmed and its role in their reactions is discussed.