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Artigo em Inglês | MEDLINE | ID: mdl-32991021


Electrocatalyzed oxidative B-H nitrogenations of nido-carborane (nido-7,8-C2 B9 H12 - ) with N-heterocycles have been established, enabling the preparation of various N-substituted nido-carboranes without chemical oxidants or metal catalyst under ambient conditions. The electrolysis manifold occurred with high levels of efficiency as well as chemo- and position- selectivity, employing sustainable electricity as the sole oxidant. The strategy set the stage for a user-friendly access to novel amino acid and fluorogenic boron-dipyrrin (BODIPY)-labeled nido-carborane hybrids.

Angew Chem Int Ed Engl ; 59(27): 11130-11135, 2020 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-32129528


A ruthenium-catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N-fused [5,6]-bicyclic heteroarenes through regioselective electrochemical C-H/N-H annulation without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.

Chemistry ; 26(15): 3241-3246, 2020 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-31875327


Electrophotochemistry has enabled arene C-H trifluoromethylation with the Langlois reagent CF3 SO2 Na under mild reaction conditions. The merger of electrosynthesis and photoredox catalysis provided a chemical oxidant-free approach for the generation of the CF3 radical. The electrophotochemistry was carried out in an operationally simple manner, setting the stage for challenging C-H trifluoromethylations of unactivated arenes and heteroarenes. The robust nature of the electrophotochemical manifold was reflected by a wide scope, including electron-rich and electron-deficient benzenes, as well as naturally occurring heteroarenes. Electrophotochemical C-H trifluoromethylation was further achieved in flow with a modular electro-flow-cell equipped with an in-operando monitoring unit for on-line flow-NMR spectroscopy, providing support for the single electron transfer processes.

J Am Chem Soc ; 141(6): 2731-2738, 2019 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-30636408


Electrochemical C-C activations were accomplished by expedient oxidative rhodium(III) catalysis. Thus, oxidative C-C alkenylations proved viable with the aid of electricity, avoiding the use of toxic and/or expensive transition-metal oxidants. The chelation-assisted C-C functionalizations proceeded with ample scope and excellent levels of chemo- and position selectivities within an organometallic C-C activation manifold. Detailed mechanistic studies provided support for a kinetically relevant C-C scission, and a well-defined organometallic rhodium(III) complex was identified as a catalytically competent intermediate. The electrochemical C-C functionalization was devoid of additional electrolytes, could be conducted on a gram scale, and provided position-selective access to densely 1,2,3-substituted arenes, which are not viable by C-H activation.

Angew Chem Int Ed Engl ; 57(20): 5828-5832, 2018 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-29633454


Rhodium(III) catalysis has enabled a plethora of oxidative C-H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we herein describe the first electrochemical rhodium-catalyzed C-H activation that avoids hazardous chemical oxidants. Environmentally benign twofold C-H/C-H functionalizations were accomplished with weakly coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant and generating H2 as the sole byproduct.