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Divergent, Stereospecific Mono- and Difluoromethylation of Boronic Esters
Valerio Fasano1, Nils Winter1, Adam Noble1
1School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
Abstract:
There is considerable interest in incorporating fluorine into agrochemicals and pharmaceuticals to improve their biological properties. Whilst a number of methods have been reported for installing CH2 F and CHF2 groups, they are mainly limited to radical reactions, which are invariably racemic. Herein, we report the divergent, stereospecific reaction of fluoroiodomethyllithium with boronic esters to give α-fluoro-boronic esters. These unique intermediates can be readily transformed into the corresponding mono- or difluoromethylated compounds through proto- or fluorodeboronation, respectively. The use of the highly unstable fluoroiodomethyllithium was key to allowing rapid 1,2-migration over competing decomposition of the carbanion. DFT calculations informed and supported the experimental findings.
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