Recently,d ual-catalytic strategies towards the decarboxylative elimination of carboxylic acids have gaineda ttention. Our lab previously reported ap hotoredox/cobaloxime dual catalytic method that allows the synthesis of enamides and enecarbamates directly from N-acyl aminoa cids and avoidst he use of any stoichiometric reagents. Further development, detailed herein, hasi mproved upon this transformation's utility and furthere xperimentation hasp rovided new insights into the reaction mechanism. These new developments and insights are anticipated to aid in the expansion of photoredox/cobalt dual-catalytic systems. Scheme1.Dual-catalytic decarboxylative olefination methods.

Supporting Information PlaceholderABSTRACT: [Cp*Rh] hydride complexes are invoked as intermediates in certain catalytic cycles, but few of these species have been successfully prepared and isolated, contributing to a relative shortage of information on the properties of such species. Here, the synthesis, isolation, and characterization of two new [Cp*Rh] hydrides are reported; the hydrides are supported by the chelating diphosphine ligands bis(diphenylphosphino)methane (dppm) and 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos). In both systems, reduction of precursor Rh(III) chloride complexes with Na(Hg) results in clean formation of isolable, formally 18e -Rh(I) species, and subsequent protonation by addition of near-stoichiometric quantities of anilinium triflate to the Rh(I) species returns high yields of the desired monohydride complexes. Single-crystal X-ray diffraction data for these compounds provide evidence of direct Rh-H interactions, confirmed by complementary infrared spectra showing Rh-H stretching frequencies at 1982 cm -1 (for the dppm-supported hydride) and 1936 cm -1 (for the Xantphos-supported hydride). Findings from comprehensive multinuclear NMR experiments reveal the properties of the unique and especially rich spin systems for the dppm-supported hydride; multifrequency NMR studies in concert with spectral simulations enabled full characterization of splitting patterns attributable to couplings involving diastereotopic methylene protons for this complex. Taken together with prior reports of related monohydrides, the results show that the reduction/protonation reaction sequence is modular for preparation of [Cp*Rh] monohydrides supported by diverse diphosphine ligands spanning from four-to eight-membered rhodacycles. ASSOCIATED CONTENT Supporting InformationNMR spectra and characterization of complexes and detailed information about performed simulations, reactivity, and X-ray crystallographic data (PDF)Cartesian coordinates (XYZ) Accession CodesCCDC 2044718-2044719 and 2067363-2067366 contain the supplementary crystallographic data for compounds 1-6. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing

New methods for C–N bond construction exploiting the N-centered electrophilic character of iminoquinones are reported. Iminoquinones, generated in situ via the condensation of o-vinylanilines with benzoquinones, undergo acid-catalyzed cyclization to afford N-arylindoles in excellent yields. Under similar reaction conditions, homoallylic amines react analogously to afford N-arylpyrroles. Additionally, organometallic nucleophiles are shown to add to the nitrogen atom of N-alkyliminoquinones to provide amine products. Finally, iminoquinones are shown to be competent electrophiles for copper-catalyzed hydroamination.

The synthesis of multimetallic compounds can enable the placement of two or more metals in close proximity, but efforts in this area are often hindered by reagent incompatibilities and a lack of selectivity. Here, we show that organometallic halfsandwich [Cp*M] (M = Rh, Ir) fragments (where Cp* is η 5 -pentamethylcyclopentadienyl) can be cleanly installed into metallomacrocyclic structures based on the workhorse diimine−monooxime−monooximato ligand system. Six new heterobimetallic compounds have been prepared to explore this synthetic chemistry, which relies on in situ protonolysis reactivity with precursor Ni(II) or Co(III) monometallic complexes in the presence of suitable [Cp*M] species. Solid-state X-ray diffraction studies confirm installation of the [Cp*M] fragments into the metallomacrocycles via effective chelation of the Rh(III) and Ir(III) centers by the nascent dioximato site. Contrasting with square-planar Ni(II) centers, the Co(III) centers prefer octahedral geometry in the heterobimetallic compounds, promoting bridging ligation of acetate across the two metals. Spectroscopic and electrochemical studies reveal subtle influences of the metals on each other's properties, consistent with the moderate M′•••M distances of ca. 3.6−3.7 Å in the modular compounds. Taken together, our results show that heterobimetallic complexes can be assembled with organometallic [Cp*M] fragments on the diimine−dioximato platform.

Polypyridyl dicarboxylates have been established as oxidatively robust ligands capable of effectively binding heavy metals, but the reductive electrochemical properties of complexes supported by these ligands have not been explored to date. Here, the redox properties of Ru(II) and uranyl(VI) (UO22+) complexes of 2,2′-bipyridyl-6,6′-dicarboxylate (bdc), 2,2′:6′,2″-terpyridyl-6,6″-dicarboxylate (tdc), and 4′-phenyl-2,2′:6′,2″-terpyridyl-6,6″-dicarboxylate (Phtdc) have been investigated, revealing that these ligands can enable both ligand- and metal-centered reductions. In control ruthenium complexes, electrochemical and spectroelectrochemical data supported by theoretical findings from density functional theory suggest electron density in the reduced forms primarily resides on the ligands. In bdc complexes of uranyl, electrochemical data and theoretical findings support the involvement of both ligand- and metal-centered reductive behavior. This “non-innocent” redox chemistry, along with support for the assertion that these ligands bind large metals effectively, suggests that polypyridyl dicarboxylates could be useful in new schemes for reductive activation of challenging metal-containing species. The observation of ligand-centered reduction events is also in agreement with the recognized “non-innocent” redox activity of related 2,2′-bipyridyl systems that lack appended carboxylate functionalities.