Organometallic reactions. Part X. The preparation and reactions of some alkynyl-lead compounds

Abstract

Trialkylalkynyl-lead compounds have been prepared by treating trialkyl-lead methoxides with alkynes, and by thermal decarboxylation of trialkyl-lead alkynylcarboxylates. The alkynyl-lead bond is more reactive than the alkyl–lead bond, and takes part in Grignard-like reactions. The alkynyl-lead compounds react with acetyl chloride to give the corresponding alkynyl methyl ketones. With aryl isocyanates, phenylethynyltriethyl-lead reacts to give a 1,3-diaryl-5-benzylidenehydantoin, which can also be prepared by ring-closure of an NN′-diaryl-N-phenylpropiolylurea, obtained by the addition of phenylpropiolic acid to a diarylcarbodi-imide. A similar ring closure, which would give 5-benzyl-1,3-diphenylhydantoin, could not be induced in N-cinnamoyl-NN′-diphenylurea.