Lewis base-directed C-H borylation reactions have received significant attention in recent years based on the synthetic versatility of the resulting organoboronate esters. Our group recently developed the phosphine-directed version of this transformation, which provides  ambiphilic phosphine boronates having a Lewis acid and Lewis base within the same proximity. Phosphino-boranes and -boronate esters have been shown to have unique reactivity as organocatalysts and bifunctional ligands. New methods to access a variety of scaffolds containing both a phosphine and a boronate ester are necessary to continue the exploration of these intriguing catalytic systems. The original method to achieve phosphine-directed C-H borylation was not found to be general, however, and required further catalyst development to expand the scope of the reaction. Two different catalysts systems were discovered with increased reactivity over the original method. The use of a cationic iridium pre-catalyst, in conjunction with pinacolborane was the most efficient transformation, resulting in high yields and selectivity for mono borylation products. The iridium-catalyzed, substrate-directed C-H borylation of a variety of aryl and benzylic phosphines will be described. The early developments of transformations that utilize the carbon-boron bond in synthetic reactions, such as oxidation to phenols and amination to aniline derivatives, will also be described.<br/>

Phosphine-directed C-H borylation reactions: New catalyst development and synthetic utility

254th National Meeting (2017)

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