Taking the F out of FLP: Simple Lewis Acid鈥揃ase Pairs for Mild Reductions with Neutral Boranes via Borenium Ion Catalysis

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• 作者：Patrick Eisenberger ; Adrian M. Bailey ; Cathleen M. Crudden
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：October 24, 2012
• 年：2012
• 卷：134
• 期：42
• 页码：17384-17387
• 全文大小：307K
• 年卷期：v.134,no.42(October 24, 2012)
• ISSN：1520-5126

文摘

Discrete three-coordinate borenium salts 1c and 1d are accessed by cooperative Lewis acid鈥揵ase pair-mediated heterolytic splitting of the B鈥揌 bond in pinacolborane by B(C₆F₅)₃路DABCO and Ph₃C⁺/DABCO, respectively. The resulting salts are competent catalysts in the reduction of a broad range of imines and can be generated in situ. Moreover, a mechanistic framework for borenium catalysis based on experimental evidence is proposed. The reaction is suggested to proceed by borenium activation of the imine substrate followed by counterintuitive hydride delivery from HBPin (with the assistance of DABCO) rather than from the HB(C₆F₅)₃^{鈥?/sup> anion, contrary to typical mechanisms of reduction in FLP systems.}