Understanding the Influence of Donor-Acceptor Diazo Compounds on the Catalyst Efficiency of B(C6F5)3 Towards Carbene Formation |
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Authors: | Mr. Rasool Babaahmadi Dr. Ayan Dasgupta Prof. Christopher J. T. Hyland Prof. Brian F. Yates Prof. Rebecca L. Melen Prof. Alireza Ariafard |
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Affiliation: | 1. School of Natural Sciences (Chemistry), University of Tasmania, Private Bag 75, Hobart, Tasmania, 7001 Australia;2. Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, Cymru/Wales UK;3. School of Chemistry and Molecular Bioscience, Molecular Horizons Research Institute, University of Wollongong, Wollongong, New South Wales, 2522 Australia |
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Abstract: | Diazo compounds have been largely used as carbene precursors for carbene transfer reactions in a variety of functionalization reactions. However, the ease of carbene generation from the corresponding diazo compounds depends upon the electron donating/withdrawing substituents either side of the diazo functionality. These groups strongly impact the ease of N2 release. Recently, tris(pentafluorophenyl)borane [B(C6F5)3] has been shown to be an alternative transition metal-free catalyst for carbene transfer reactions. Herein, a density functional theory (DFT) study on the generation of carbene species from α-aryl α-diazocarbonyl compounds using catalytic amounts of B(C6F5)3 is reported. The significant finding is that the efficiency of the catalyst depends directly on the nature of the substituents on both the aryl ring and the carbonyl group of the substrate. In some cases, the boron catalyst has negligible effect on the ease of the carbene formation, while in other cases there is a dramatic reduction in the activation energy of the reaction. This direct dependence is not commonly observed in catalysis and this finding opens the way for intelligent design of this and other similar catalytic reactions. |
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Keywords: | carbene density functional theory (DFT) diazo compounds Lewis acid catalysis mechanistic study tris(pentafluorophenyl)borane |
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