C,C- AND C,N-LINKED DIMERS AND 4-ARYLMETHYL DERIVATIVES FROM 4-ARYLMETHYLENE PYRAZOL-5-ONES AND ISOXAZOL-5-ONES WITH 2-ARYLBENZIMIDAZOLINES

2-arylbenzimidazolines (8), generated in situ from o-phenylenediamine (7) and the appropriate arylaldehydes, by reaction with 4-arylmethylen e pyrazol-5-ones (1) or isoxazol-5-ones (2) produce the 4-arylmethyl d erivatives (3) or (4) and the C,C- (5) or the C,N-linked dimers. The r eaction was rationalised on the basis of the role of 2-arylbenzimidazo line as a reducing agent and proceeds by a non-chain, free radical pro cess involving one-electron transfer.