1H-Pyrroles can be directly functionalized by means of the incorporation of carbene groups from diazo compounds, in a process catalyzed by Tp x Cu complexes (Tp x = hydrotrispyrazolylborate ligand). The reactions take place with a complete selectivity toward the formal insertion of the carbene into the C-H bond, leading to alkylated pyrroles, with no modification of the C-H, N-H or C=C bonds of the pyrrole unit. Alkyl substituents at C-ring as well as alkyl, aryl, allyl or alkyne substitution at N atom are tolerated, the strategy affording 20 new pyrrole derivatives. The observance of partial deuteration at the methylene group when the reaction is carried out with added D 2 O serves to discard the direct insertion of the carbene group into the C sp2 -H bond, the alternative electrophilic attack to the pyrrole ring being feasible.

The direct functionalization of Si–H bonds by the nitrene insertion methodology is described. A copper(I) complex bearing a trispyrazolylborate ligand catalyzes the transfer of a nitrene group from PhI=NTs to the Si–H bond of silanes, disilanes, and siloxanes, leading to the exclusive formation of Si–NH moieties in the first example of this transformation. The process tolerates other functionalities in the substrate such as several C–H bonds and alkyne and alkene moieties directly bonded to the silicon center. Density functional theory (DFT) calculations provide a mechanistic interpretation consisting of a Si–H homolytic cleavage and subsequent rebound to the Si-centered radical.

In the context of copper-catalyzed nitrene transfer to olefins, many systems operate upon mixing a CuX salt (X = halide, OTf) and a polydentate N-based ligand, assuming that the X ligand is displaced from the coordination sphere toward a counterion position. Herein, we demonstrated that such general assumption should be in doubt since studies carried out with the well-defined copper(I) complexes (TTM)CuCl and [(TTM)Cu-(NCMe)]PF 6 (TTM = tris(triazolyl)methane ligand) demonstrate a dual behavior from a catalytic and mechanistic point of view that exclusively depends on the presence or absence of the chloride ligand bonded to the metal center. When coordinated, the turnover-limiting step corresponds to the formation of the carbon−nitrene bond, whereas in its absence, the highest barrier corresponds to the formation of the copper−nitrene intermediate.

The catalytic functionalization of pyrroles by incorporation of a nitrene group is reported. The Cα-H bond of 1H-pyrrole is amidated upon the formal insertion of the NTs (Ts = p-toluenesulfonyl) group catalyzed by Tp Br3 Cu (NCMe) (Tp Br3 = hydrotris(3,4,5-tribromo-pyrazolyl)borate). N-substituted pyrroles also verify the same transformation. The mechanism proposal is similar to that previously described for benzene amidation with the same catalyst and PhI=NTs, which takes place through aziridine formation, ring opening and 1,2-hydrogen shift. A cascade reaction involving the coupling of 2,5-dimethylfuran, 1,2,3-trimethyl-pyrrole and a nitrene NTs group is also described, leading to a 1,2dihydropyridine-imine compound. Scheme 1. Most common CÀ N bond formation by metal catalysed nitrene insertion: olefin aziridination and CÀ H amidation. Scheme 2. Left: potential reaction sites toward attack by the metalÀ nitrene species. This work: the reaction with 1H-or Nsubstituted pyrroles takes place onto the C sp2 À H bond in an exclusive manner. Scheme 4. Substituted pyrroles as substrates. Scheme 5. Competition experiments toward relative reactivity.

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