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Departmental SeminarStephen A. Westcott
Department of Chemistry and Biochemistry, Mount Allison University
Fri, April 22, 2016, 2:00 pm
To B-E or not to B-E? Developing the Phosphinoboration Reaction
Over the past two decades, the transition metal catalysed addition of boron-element (B-E, where E = H, B, Sn, Si, etc) bonds to unsaturated compounds has received a considerable amount of attention. Given the intensity of interest in the reactivity of B-E bonds it is somewhat surprising that relatively little is known about the analogous addition chemistry of compounds containing single B-E bonds where E is phosphorus. The corresponding phosphinoboration would introduce a P-C bond and a reactive B-C bond that could be further elaborated to provide access to a host of useful structural motifs and, in this regard, is a worthy target. The synthesis of phosphinoboronate esters containing a single P-B bond is reported herein, together with reactivity studies towards a range of organic substrates. We also discuss the transition metal catalysed phosphinoboration of C-C multiple bonds in which P-C and B-C bonds are formed in a single step; allenes react via a highly regioselective 1,2-addition while terminal alkynes give products where both P and B groups have added to the same carbon atom.