Keele Research Repository

This thesis is concerned with the investigation of the reactions of some trivalent phosphorus compounds with electrophilic acetylenes, and in particular dimethyl acetylenedicarboxylate.
These studies have involved extensive use of nuclear magnetic resonance (n.m.r.) spectroscopy to monitor reaction pathways and to identify intermediates.
The nature of the 1:1 intermediate initially formed in the reaction of a trivalent phosphorus compound, such as a trialkyl phosphite, with dimethyl acetylenedicarboxylate has been studied and shown to exhibit both anionic and carbenoid character.
The reaction of these 1:1 intermediates with further dimethyl acetylenedicarboxylate leads to the formation of unstable ylides which rearrange at room temperature to cyclic ylides via five-coordinate phosphoranes. Both these latter two species have been shown to be valuable precursors for the preparation of some novel oxo-phospholes.
The 1:1 intermediates from trialkyl phosphites react with carbon dioxide to form "C02-adducts" which react with further trialkyl phosphite to give ylides. These ylides have been shown to provide convenient synthetic routes to some phosphonates and substituted furans which would otherwise be difficult to prepare.
The progress of the carbon dioxide in these reaction pathways has been investigated by 13C n.m.r. spectroscopy, by using 13C isotopically labelled carbon dioxide.