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Electrophilic boron carboxylate and phosphinate complexes

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Abstract

The reactions of a series of carboxylic acids with H2B(C6F5)·SMe2 are shown to afford species of the form [RC(O)OB(C6F5)]2O, (R = Tol 1, Ph 2, C6F5 3, Me2BrC 4, Me 5) in 87–95% yields with the concurrent reduction of the carboxylic acid to the corresponding aldehyde. A mechanism for the formation of 1–5 is proposed to proceed via a cyclic eight-membered ring species. Analogues of these species were prepared via reactions of carboxylic and phosphinic acids with HB(C6F5)2 and H2B(C6F5)·SMe2, respectively, to give [TolC(O)OB(C6F5)2]2 6, [(C6F5)C(O)OB(C6F5)2]2 7, and [Ph2P(O)OBH(C6F5)]2 8. These products react subsequently to give TolC(O)OBH(C6F5)(NC5H4NMe2) 9 and Ph2P(O)OBH(C6F5)(NC5H4NMe2) 10. The acyloxyborate derivatives 1–4 were shown to be inactive in mediating the direct amidation of carboxylic acids, consistent with previous observations that infer the need for a sterically congested environment about the boron centres.

Graphical abstract: Electrophilic boron carboxylate and phosphinate complexes

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Publication details

The article was received on 06 Dec 2018, accepted on 08 Jan 2019 and first published on 09 Jan 2019


Article type: Paper
DOI: 10.1039/C8DT04818E
Citation: Dalton Trans., 2019, Advance Article
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    Electrophilic boron carboxylate and phosphinate complexes

    D. Zhu, J. H. W. LaFortune, R. L. Melen and D. W. Stephan, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C8DT04818E

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