Azoxy cpds prepn by reducing nitro cpds - using polystyrene-supported metal complex catalyst, giving high yields

摘要

Catalytic reduction of aromatic nitro cpds. into azoxy derivs. is effected by reaction in an anhydrous alcohol (pref. EtOH) under an inert atmos with a strongly reducing hydrogen cpd. (pref. NaBH4) in presence of a polystyrene supported metal complex catalyst of formula (I): where L is -CH2-PPh2 or -PPh2; M is Ni(prefd) or Co; X is Cl (prefd.) or Br), the polystyrene being a homopolymer or copolymer with a divinyl aromatic cpd. The prods. are inters., e.g. for dyes. The process gives high yields (e.g. 35-85% c.f. 15% with unsupported PPh2NiCl2 catalyst) of pure product. Catalyst may be recovered and reused.