Nitrene

About: Nitrene is a research topic. Over the lifetime, 2111 publications have been published within this topic receiving 49777 citations.

Metal-catalyzed nitrogen-atom transfer methods for the oxidation of aliphatic C-H bonds.

Abstract: For more than a century, chemists have endeavored to discover and develop reaction processes that enable the selective oxidation of hydrocarbons. In the 1970s, Abramovitch and Yamada described the synthesis and electrophilic reactivity of sulfonyliminoiodinanes (RSO2N═IPh), demonstrating the utility of this new class of reagents to function as nitrene equivalents. Subsequent investigations by Breslow, Mansuy, and Muller would show such oxidants to be competent for alkene and saturated hydrocarbon functionalization when combined with transition metal salts or metal complexes, namely those of Mn, Fe, and Rh. Here, we trace our own studies to develop N-atom transfer technologies for C–H and π-bond oxidation. This Account discusses advances in both intra- and intermolecular amination processes mediated by dirhodium and diruthenium complexes, as well as the mechanistic foundations of catalyst reactivity and arrest. Explicit reference is given to questions that remain unanswered and to problem areas that are ri...

Olefin Cyclopropanation via Carbene Transfer Catalyzed by Engineered Cytochrome P450 Enzymes

Abstract: Transition metal–catalyzed transfers of carbenes, nitrenes, and oxenes are powerful methods for functionalizing C=C and C–H bonds. Nature has evolved a diverse toolbox for oxene transfers, as exemplified by the myriad monooxygenation reactions catalyzed by cytochrome P450 enzymes. The isoelectronic carbene transfer to olefins, a widely used C–C bond–forming reaction in organic synthesis, has no biological counterpart. Here we report engineered variants of cytochrome P450BM3 that catalyze highly diastereo- and enantioselective cyclopropanation of styrenes from diazoester reagents via putative carbene transfer. This work highlights the capacity to adapt existing enzymes for the catalysis of synthetically important reactions not previously observed in nature.

Intermolecular Amidation of Unactivated sp2 and sp3 C−H Bonds via Palladium-Catalyzed Cascade C−H Activation/Nitrene Insertion

Abstract: This communication describes the Pd(OAc)2-catalyzed intermolecular amidation reactions of unactivated sp2 and sp3 C−H bonds using primary amides and potassium persulfate. The substrates containing a pendent oxime or pyridine group were amidated with excellent chemo- and regioselectivities. It is noteworthy that reactive C−X bonds were well-tolerated and a variety of primary amides can be effective nucleophiles for the Pd-catalyzed C−H amidation reactions. For the reaction of unactivated sp3 C−H bonds, β-amidation of 1° sp3 C−H bonds versus 2° C−H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C−H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated complex.

Catalytic C–H functionalization by metalloporphyrins: recent developments and future directions

Abstract: Metalloporphyrins are a class of versatile catalysts with the capability to functionalize saturated C–H bonds via several well-defined atom/group transfer processes, including oxene, nitrene, and carbene C–H insertions. The corresponding hydroxylation, amination, and alkylation reactions provide direct approaches for the catalytic conversion of abundant hydrocarbons into value-added functional molecules through C–O, C–N, and C–C bond formations, respectively. This tutorial review describes metalloporphyrin-based catalytic systems for the functionalization of different types of sp3 C–H bonds, both inter- and intramolecularly, including challenging primary C–H bonds. Additional features of metalloporphyrin-catalyzed C–H functionalization include unusual selectivities and high turnover numbers.