The copper complex Tp (CF3)2,Br Cu(NCMe) (1, Tp (CF3)2,Br = hydrotris((3,5-bis(trifluoromethyl)-4-bromo)-pyrazol-1-yl)borate) catalyzes the insertion of the CHCO 2 Et group (from ethyl diazoacetate N 2 CHCO 2 Et, EDA) into the C-H bonds of methane, in a homogeneous process that uses supercritical carbon dioxide (scCO 2 ) as the reaction medium.Other light alkanes such as ethane, propane and butane have been also functionalized with this copper-based catalyst, in the first example of the derivatization of the series of C 1 -C 4 alkanes with this metal with a soluble catalyst.

We report quantitative measurements of the relative reactivities of a series of C-H bonds of gaseous or liquid C H alkanes (n=1-8, 29 different C-H bonds) towards in situ generated electrophiles (copper, silver, and rhodium carbenes), with methane as the reference. This strategy surpasses the drawback of previous model reactions of alkanes with strong electrophiles suffering from C-C cleavage processes, which precluded direct comparison of the relative reactivities of alkane C-H bonds.

Di- and trinuclear complexes of copper(I) bearing bis- or tris-N-heterocyclic carbene ligands have been prepared and evaluated as catalysts in nitrene transfer reactions from PhI=NTs to unsaturated and saturated substrates (olefin aziridination and C–H bond amidation) and carbene transfer reactions from diazo compounds to olefins. The complexes exhibited moderate-to-high catalytic activity in both processes. The tosylamidation of C–H bonds, previously unreported with a NHC-containing copper catalyst, was promoted by the dinuclear complexes

A series of alkanes CnH2n+2 have been functionalized in water as the reaction medium, using a silver-based catalyst, upon insertion of carbene (CHCO2Et from N2CHCO2Et) groups into their carbon-hydrogen bonds of hexane, cyclohexane or 2-methylbutane, among others. The regioselectivity toward the distinct reaction sites is identical to that found in neat alkane, the water-based system allowing the use of a much shorter excess of the hydrocarbon. This is the first example of the intermolecular functionalization of alkanes with this strategy in water. The functionalized alkanes partially undergoes a incorporation of a second carbene unit to provide -(acyloxy)acetates, in an unprecedented tandem reaction of this nature.

The functionalization of the primary sites of alkanesi so ne of the more challenginga reas in catalysis. In this context, an ovel effect has been discovered that is responsible for an enhancement in the reactivity of the primary CÀHb onds of alkanes in ac atalytic system. The copperc omplex Tp (CF 3 ) 2 ,Br Cu(NCMe) (Tp (CF 3 ) 2 ,Br = hydrotris{[3,5-bis(trifluoromethyl)-4-bromo]-pyrazol-1-yl}borate) catalyzes the functionalization of C n H 2n + 2 with ethyl diazoacetate upon inserting the CHCO 2 Et unit into CÀH bonds. In addition, the selectivity of the reactiont oward the primarys ites significantly increased relative to that obtained in neat alkane upon using supercritical carbon dioxide as ther eaction medium. This was attributed to the effect of the carbon dioxide molecules that withdraw electron density from the fluorine atoms of the ligand, which enhances the electrophilic nature of the metal center. DFT studies validated this proposal.The catalytic selective functionalizationofnonactivated alkanes C n H 2n + 2 remains one of the challenges in currentc hemistry. [1, 2] In spite of decades of effort towardt hat end, very few examples (e.g.,e lectrophilic activation, [3] dehydrogenation, [4] silylation, [5] and borylation [6] )o fm etal-catalyzed transformationso f these compounds into value-added products have been described (Scheme 1). This lack of successc an be explained not only in terms of their inertness (mainly because of their poor s nucleophilicity,t heir high bond dissociation energies, [7] and their low polarity) but also in terms of the unavailability of further subsequentt ransformationst hat provide neat functionalization. Moreover,f unctionalization of the primary sites in ap referential manner is even more difficult to achieve. In fact, only the alkane borylation catalytic systemd eveloped by Hartwig and co-workers [6] could be considered as selective toward the terminal CÀHb onds of alkanes.There is af actor that is common to the examples shown in Scheme 1: the interaction of the reactingC ÀHb ond with the metal center. Actually,t his is the origin of the small number of catalytic systems for alkanef unctionalization:i nm any cases, the formation of very stable metal-carbon and/orm etal-hydride bond(s) precludest he intermediate from going further into the functionalization step. An alternative approach consists of the design of catalytic systemsi nw hich the CÀHb ond interacts with an Xl igand,v ery often as parto fa ni nsitu generated unsaturated M=Xb ond, and not with the metal center.[8] This is the basis of as eries of catalytic systems in which C n H 2n + 2 molecules have been functionalized by the neat, formal insertion of carbene, nitrene, or oxo units into their CÀHb onds (Scheme 2). Group 11 metal based catalysts have been found as efficient catalysts for those transformations, [9] particularly if they contain pyrazolylborate ligands. In an example of the potentialo ft his strategy,w ef irst described silver-based catalysts containing highly fluorinated trisindazolylborate l...