The use of transition-metal-based catalysts for the transfer of carbene units from diazo compounds constitutes a powerful tool in organic synthesis.[1] Several metals have been reported to mediate this transformation effectively, and the appropriate selection of ligands has permitted excellent selectivities. Highly chemo-, diastereo-, and/or enantioselective systems have been reported with rhodium-, copper-, or cobaltcontaining catalysts. In fact, nearly all 12 elements of Groups 8-11 have been found to decompose diazo compounds and transfer a carbene unit to saturated or unsaturated organic substrates, [2] leading to the insertion or addition product, respectively (Scheme 1). Only one of these 12 elements remains unexplored in this chemistry: gold. [3] Although the other members of Group 11-copper and, to a lesser extent, silver-have been described to induce such transformations, conducting this type of catalytic reaction with gold remains a challenge. We therefore focused our attention on the development of a gold-based catalyst, as a result of our experience in the area of metal-catalyzed carbene transfer from ethyl diazoacetate (EDA). [4] We recently reported the catalytic behavior of [(IPr)CuCl] (1, IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene) for the transfer of carbene from ethyl diazoacetate to olefins, amines, and alcohols to form cyclopropanes, amino acid derivatives, and ethers, respectively.[5]

A simple copper-based catalytic system has been developed for the carbon-hydrogen amidation reaction. The copper-homoscorpionate complex Tp(Br3)Cu(NCMe) catalyzes the transfer of the nitrene unit NTs (Ts = p-toluenesulfonyl) and its subsequent insertion into the sp(3) C-H bonds of alkyl aromatic and cyclic ethers or the sp(2) C-H bonds of benzene using PhI=NTs as the nitrene source, affording the corresponding trisubstitued NR(1)HTs amines in moderate to high yields. The use of the environmentally friendly chloramine-T has also proven effective, with the advantage that sodium chloride is formed as the only byproduct. A tandem, one-pot consecutive nitrene-carbene insertion system has been developed to yield amino acid derivatives.

Facile alkane functionalization by means of the insertion of :CHCO 2 Et, from ethyl diazoacetate, into carbon-hydrogen bonds mediated by catalytic amounts of (NHC)MCl (NHC ) N-heterocyclic ligand; M ) Cu, Au) and a halide scavenger MX has been achieved. This chemistry includes the insertion of the carbene fragment into alkane primary positions with Cu-and Au-based catalysts. The nature of the counterion X and of the NHC ligand have a significant effect on the overall yields and regioselectivity of the reaction.

The complexes [Cu(NHC)(NCMe)]BF4 (NHC=N-heterocyclic ligand), with bis(catecholato)diboron (B2(cat)2) as the boron source, efficiently catalyze the diboration of styrene with very high degrees of conversion. With the appropriate NHC ligand, the reaction proceeds quantitatively toward the diborated derivative PhCH(Bcat)--CH2(Bcat). The [styrene]/[B2(cat)2] ratio also has a strong effect on the selectivity: the use of an excess of styrene allows modification of the selectivity toward the formation solely of the monoborated derivative, PhCH2--CH2(Bcat). DFT calculations suggest that no oxidative addition processes take place at copper, but that intermediates containing coordinated sigma-bonds are involved in the catalytic cycle.

A number of cationic gold(I) complexes have been synthesized and found to be stabilized by the use of N-heterocyclic carbene ligands. These species are often employed as in situ-generated reactive intermediates in gold catalyzed organic transformations. An isolated, well-defined species was tested in gold-mediated carbene transfer reactions from ethyl diazoacetate.

The use of transition-metal-based catalysts for the transfer of carbene units from diazo compounds constitutes a powerful tool in organic synthesis.[1] Several metals have been reported to mediate this transformation effectively, and the appropriate selection of ligands has permitted excellent selectivities. Highly chemo-, diastereo-, and/or enantioselective systems have been reported with rhodium-, copper-, or cobaltcontaining catalysts. In fact, nearly all 12 elements of Groups 8-11 have been found to decompose diazo compounds and transfer a carbene unit to saturated or unsaturated organic substrates, [2] leading to the insertion or addition product, respectively (Scheme 1). Only one of these 12 elements remains unexplored in this chemistry: gold. [3] Although the other members of Group 11-copper and, to a lesser extent, silver-have been described to induce such transformations, conducting this type of catalytic reaction with gold remains a challenge. We therefore focused our attention on the development of a gold-based catalyst, as a result of our experience in the area of metal-catalyzed carbene transfer from ethyl diazoacetate (EDA). [4] We recently reported the catalytic behavior of [(IPr)CuCl] (1, IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene) for the transfer of carbene from ethyl diazoacetate to olefins, amines, and alcohols to form cyclopropanes, amino acid derivatives, and ethers, respectively.[5]

RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) TITLE RUNNING HEAD Gold-catalyzed arene C-H bonds functionalization by carbene insertion.ABSTRACT. The direct functionalization of aromatic C-H bonds by carbene insertion from diazocompounds catalyzed by gold complexes with N-heterocyclic ligands is described. The reaction is completely selective toward the Csp 2 -H bonds, other Csp 3 -H bonds remaining unreacted. A study with a several NHC ligands in Au(I) and Au(III) complexes has been performed. A potential application in profen derivatives has also been developed.

The catalytic functionalization of the Csp 2-H bond of benzene by means of the insertion of the CHCO2Et group from ethyl diazoacetate (N2=CHCO2Et) has been studied with the series of coinage metal complexes IPrMCl (IPr = IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene) and NaBAr F 4 (BAr F 4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate). For Cu and Ag, these examples constitute the first of such metals toward this transformation, that also provides ethyl cyclohepta-2,4,6-trienecarboxylate as by-product from the so-called Buchner reaction. In the case of methyl-substituted benzenes, the reaction exclusively proceeds onto the aromatic ring, the Csp 3-H bond remaining unreacted. A significant coinage metal effect has been observed, since the gold catalyst favors the formation of the insertion product into Csp 2-H bond whereas copper and silver preferentially induce the formation of the cycloheptatriene derivative. Experimental studies and theoretical calculations have explained the observed selectivity in terms of the formation of a common Wheland intermediate, resembling an electrophilic aromatic substitution, from which the reaction pathway evolves into two separate routes to each product.