Rh2(II,III) Catalysts with Chelating Carboxylate and Carboxamidate Supports: Electronic Structure and Nitrene Transfer Reactivity.

Dirhodium-catalyzed C-H amination is hypothesized to proceed via Rh2-nitrene intermediates in either the Rh2(II,II) or Rh2(II,III) redox state. Herein, we report joint theoretical and experimental studies of the ground electronic state (GES), redox potentials, and C-H amination of [Rh2(II,III)(O2CCH3)4(L)n](+) (1_L) (L = none, Cl(-), and H2O), [Rh2(esp)2](+) (2), and Rh2(espn)2Cl (3) (esp = α,α,α',α'-tetramethyl-1,3-benzenedipropanoate and espn = α,α,α',α'-tetramethyl-1,3-benzenedipropanamidate). CASSCF calculations on 1_L yield a wave function with two closely weighted configurations, (δ*)(2)(π1*)(2)(π2*)(1) and (δ*)(2)(π1*)(1)(π2*)(2), consistent with reported EPR g values [Chem.

Direct spectroscopic characterization of a transitory dirhodium donor-acceptor carbene complex.

A multitude of organic transformations catalyzed by dirhodium(II) (Rh2) complexes are thought to proceed via the intermediacy of highly reactive, electrophilic carbenoid intermediates that have eluded direct observation. Herein, we report the generation of a metastable Rh2-carbenoid intermediate supported by a donor-acceptor carbene fragment. This intermediate is stable for a period of ~20 hours in chloroform solution at 0°C, allowing for an exploration of its physical and chemical properties.

Introducing a mixed-valent dirhodium(II,III) catalyst with increased stability in C-H amination.

A new mixed-valent Rh(2)(II,III) dimer, [Rh(2)(espn)(2)Cl] (espn(2-) = α,α,α',α'-tetramethyl-1,3-benzenedipropanamidate), is reported. This compound readily dissociates Cl(-) at low concentrations in solution to form the active [Rh(2)(espn)(2)](+) catalyst, which performs intramolecular C-H amination with TONs > 1400. This work expands the scope of Rh(2)(II,III) dimers to nitrenoid chemistry.

Evidence for a one-electron mechanistic regime in dirhodium-catalyzed intermolecular C-H amination.

Swift and energy efficient conversion of chemical feedstocks to pharmaceuticals and agrochemicals requires the development of new methods to add nitrogen functionality to unfunctionalized organic substrates. Dirhodium-catalyzed insertion of nitrene species into C-H bonds is a promising new method, the main drawback of which is the currently limited understanding of the catalytic mechanism. Herein, cyclic voltammetry and controlled potential electrolysis measurements have enabled us to solve many of the mechanistic mysteries of intermolecular C-H amination catalyzed by [Rh(2)(esp)(2)] (esp=α,α,α',α'-tetramethyl-1,3-benzenedipropanoate).

Bioactivation of phencyclidine in rat and human liver microsomes and recombinant P450 2B enzymes: evidence for the formation of a novel quinone methide intermediate.

The hypothesis that the psychological side effects associated with the anesthetic phencyclidine (PCP) may be caused by irreversible binding of PCP or its reactive metabolite(s) to critical macromolecules in the brain has resulted in numerous in vitro studies aimed at characterizing pathways of PCP bioactivation. The studies described herein extend the current knowledge of PCP metabolism and provide details on a previously unknown metabolic activation pathway of PCP. Following incubations with NADPH- and GSH-supplemented human and rat liver microsomes and recombinant P450 2B enzymes, two sulfhydryl conjugates with MH+ ions at 547 and 482 Da, respectively, were detected by LC/MS/MS.