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Abstract A nickel‐catalyzed asymmetric diarylation reaction of vinylarenes enables the preparation of chiral α,α,β‐triarylated ethane scaffolds, which exist in a number of biologically active molecules. The use of reducing conditions with aryl bromides as coupling partners obviates the need for stoichiometric organometallic reagents and tolerates a broad range of functional groups. The application of anN‐oxyl radical as a ligand to a nickel catalyst represents a novel approach to facilitate nickel‐catalyzed cross‐coupling reactions.
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Abstract The incorporation of CO2into organometallic and organic molecules represents a sustainable way to prepare carboxylates. The mechanism of reductive carboxylation of alkyl halides has been proposed to proceed through the reduction of NiIIto NiIby either Zn or Mn, followed by CO2insertion into NiI‐alkyl species. No experimental evidence has been previously established to support the two proposed steps. Demonstrated herein is that the direct reduction of (tBu‐Xantphos)NiIIBr2by Zn affords NiIspecies. (tBu‐Xantphos)NiI‐Me and (tBu‐Xantphos)NiI‐Et complexes undergo fast insertion of CO2at 22 °C. The substantially faster rate, relative to that of NiIIcomplexes, serves as the long‐sought‐after experimental support for the proposed mechanisms of Ni‐catalyzed carboxylation reactions.more » « less
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null (Ed.)Alkenes are an appealing functional group that can be transformed into a variety of structures. Transition-metal catalyzed dicarbofunctionalization of alkenes can efficiently afford products with complex substitution patterns from simple substrates. Under reductive conditions, this transformation can be achieved while avoiding stoichiometric organometallic reagents. Asymmetric difunctionalization of alkenes has been underdeveloped, in spite of its potential synthetic utility. Herein, we present a summary of our efforts to control enantioselectivity for alkene diarylation with a nickel catalyst. This reaction is useful for preparing triarylethanes. The selectivity is enhanced by an N-oxyl radical additive.more » « less
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A reductive dicarbofunctionalization reaction of alkenes has been developed and applied to the preparation of substituted carbo- and heterocycles. The reaction conditions avoid the use of air-sensitive organometallic reagents, and are compatible with a broad range of bromo-electrophiles and a wide variety of substituents to give cyclic products in excellent yields.more » « less
