I t has to be emphasised that efficiency of conversion 1—> 2 depends on the structure of hydrazine derivative and reaction conditions. Phenylhydrazine reacts with 1 in pyridine solution giving 2 in almost quantitative yield [both (Z)-and (E)-isomers are present as evidenced by 1 'PN. l\/iR]. In the same solvent, unsymmetrical N, N-dimethylh4ydrazine reacts with 1 giving, in addition to the corresponding 2, the products of P—~ C bond ...