Hydride as a Leaving Group in the Reaction of Pinacolborane with Halides under Ambient Grignard and Barbier Conditions. One-Pot Synthesis of Alkyl, Aryl, Heteroaryl, Vinyl, and Allyl Pinacolboronic Esters
Jacob W. Clary, Terry J. Rettenmaier, Rachel Snelling, Whitney Bryks, Jesse Banwell, W. Todd Wipke and Bakthan Singaram*
*Department of Chemistry and Biochemistry, University of California, Santa Cruz, 1156 High Street, Santa Cruz, California, 95064, Email: singaramchemistry.ucsc.edu
J. W. Clary, T. J. Rettenmaier, R. Snelling, W. Bryks, J. Banwell, W. T. Wipke, B. Singaram, J. Org. Chem., 2011, 76, 9602-9610.
DOI: 10.1021/jo201093u (free Supporting Information)
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Aliphatic, aromatic, heteroaromatic, vinyl, or allylic Grignard reagents react with pinacolborane at ambient temperature in tetrahydrofuran to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide and affords the product boronic ester in very good yield. This reaction also can be carried out under Barbier conditions.
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