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Phosphonium salts. I. The alkaline hydrolysis of some bis-phosphonium salts

1969; CSIRO Publishing; Volume: 22; Issue: 7 Linguagem: Inglês

10.1071/ch9691385

1445-0038

JJ Brophy, MJ Gallagher,

Synthetic Organic Chemistry Methods

Ethane- and ethene-1,2-bisphosphonium salts are cleaved by alkali into a phosphine and a phosphine oxide with loss of the two-carbon bridge. When the phosphorus atom carries benzyl substituents, loss of the benzyl groups is competitive with loss of the bridge. ��� Based on a kinetic study, a synchronous mechanism, analogous to the alkaline hydrolysis of acyclic monophosphonium salts, is proposed to account for the fragmentation. ��� With 6-membered 1,4-diphosphonio heterocyclic salts the nature of the products is dependent on whether alkali or phosphonium salt is present in excess. With an excess of alkali a synchronous mechanism again appears to operate, while with an excess of salt the reaction proceeds stepwise and without loss of the bridge. A partial explanation of these facts is advanced in terms of non-bonded interactions in the intermediate phosphoranes. ��� The synchronous reaction appears to be favoured by coplanarity of the P-C-C-P system.