Conditions for deuterium exchange mediated by iridium complexes formed in situ
作者:Paul W.C Cross、George J Ellames、Jennifer S Gibson、John M Herbert、William J Kerr、Alan H McNeill、Trevor W Mathers
DOI:10.1016/s0040-4020(03)00422-8
日期:2003.4
incorporation into a number of substrate classes has been achieved. The electronic properties and number of ligands at the metal centre are instrumental in determining which catalysts are best suited to exchange in any given substrate.
Iridium-Catalyzed C–H Activation and Deuteration of Primary Sulfonamides: An Experimental and Computational Study
作者:William J. Kerr、Marc Reid、Tell Tuttle
DOI:10.1021/cs5015755
日期:2015.1.2
Iridium-catalyzed C-H activation and ortho-hydrogen isotope exchange is an important technology for allowing access to labelled organic substrates and aromatic drug molecules, and for the development of further C-H activation processes in organic synthesis. The use of [(COD)Ir(NHC)Cl] complexes (NHC = N-heterocyclic carbene) in the ortho-deuteration of primary sulfonamides under ambient conditions is reported. This methodology has been applied to the deuteration of a series of substrates, including the COX-2 inhibitors Celecoxib and Mavacoxib, demonstrating selective complexation of the primary sulfonamide over a competing pyrazole moiety. The observed chemoselectivity can be reversed by employing more encumbered catalyst derivatives of the type [(COD)Ir(NHC)(PPh3)]PF6. Computational studies have revealed that, although C-H activation is rate-determining, substrate complexation or subsequent C-H activation can be product-determining depending on the catalyst employed.
Isotopic Labelling of Functionalised Arenes Catalysed by Iridium(I) Species of the [(cod)Ir(NHC)(py)]PF6 Complex Class
Iridium(I) complexes of the type [(cod)Ir(NHC)(Py)]PF6 have been exposed as efficient catalysts in the area of hydrogen-isotope exchange. More specifically, by an ortho-directed C-H activation process, high levels of deuterium incorporation have been achieved using low levels of catalyst over a range of functionalised aromatic compounds. Additionally, the developed protocol has been extended to include a selected pharmacological target, where chemoselective labelling is observed within such a multifunctional substrate.