Synthesis, characterization, reactivity, and computational studies of a novel phosphinoboronate ester

Abstract

Only in recent years have single bond phosphinoboronate esters gained attention as an efficient method to simultaneously add both a phosphino group and a boron group to unsaturated functionalities. To date only a handful have been characterized and their reactivity remains underexplored. This work reports upon the synthesis and reactivity of the novel phosphinoboronate ester Ph2PBbzpin (1, bzpin = O2C2Ph4) with aldehydes, ketones, and a,b-unsaturated carbonyls. In general, it was found that most reactions result in 1,2-addition products with the formation of new P-C and B-O bonds. Novel reactivity is observed when bulkier ketones are employed and alternatively the formation of a boron enolate and free diphenyl phosphine are observed. Through experimental and computational studies, we found that product selectivity is highly dependent upon steric effects.