Herein we report a combined experimental and theoretical study on the deuterium labelling of benzoate ester derivatives, utilizing our developed iridium N-heterocyclic carbene/phosphine catalysts. A range of benzoate esters were screened, including derivatives with electron-donating and -withdrawing groups in the para- position. The substrate scope, in terms of the alkoxy group, was studied and the nature of the catalyst counter-ion was shown to have a profound effect on the efficiency of isotope exchange. Finally, the observed chemoselectivity was rationalized by rate studies and theoretical calculations, and this insight was applied to the selective labelling of benzoate esters bearing a second directing group.
Hydrogen isotope exchange with highly active iridium(I) NHC/phosphine complexes: a comparative counterion study
作者:William J. Kerr、Richard J. Mudd、Philippa K. Owens、Marc Reid、Jack A. Brown、Sebastien Campos
DOI:10.1002/jlcr.3427
日期:2016.12
present a range of substrates that undergo hydrogenisotopeexchange with an iridium(I) N-heterocyclic carbene/phosphine complex bearing the less coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate counterion and compare these with labelling using the equivalent, more established hexafluorophosphate complex. The changes in reactivity and selectivity of these complexes in a series of solvents