A novel unsymmetrical sp2-sp3 diboron compound has been developed for the copper-catalyzed b-boration of a,b-unsaturated conjugated compounds.  The mild reaction conditions allow boration of a variety of substrates including a,b-unsaturated esters, ketones, nitriles, ynones, amides and aldehydes in the absence of additives such as phosphine and sodium tert-butoxide.  The presence of an sp3 hybridized  boron center, unambigously confirmed by X-ray crystallography, sufficiently activates the unsymmetrical PDIPA diboron compound 2 to transfer chemoselectively its sp2 hybridized boron to the substrate.  These observations suggest that the activation of one of the boron atoms is an essential step in the b-boration catalytic cycle.

Preactivated unsymmetrical diboron: Catalytic regioselective boration of α,β-unsaturated conjugated compounds

240th National Meeting (2010)

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