An improved synthesis of the two triarylsubstituted phospha-alkenes mesityl (diphenylmethylene) phosphine (la) and 2, 6dimethylphenyl (diphenylmethylene) phosphine (lb) is described. Of several variants, the preferred route starts with the aryl bromides 4 which are converted to the corresponding Grignard reagents and to the arylphosphonous diamides 7 which with PCl3, yield arylphosphonous amide chlorides 9 thence phosphinous amides ...