Efficient Homogeneous Catalysis in the Reduction of CO₂ to CO

The well-defined copper(I) boryl complex [(IPr)Cu(Bpin)] [where IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, and pin = pinacolate:  2,3-dimethyl-2,3-butanediolate] deoxygenates CO2 rapidly and quantitatively, affording CO and the borate complex [(IPr)Cu(OBpin)]. The boryl may be regenerated by treatment with the diboron compound pinB−Bpin, giving the stable byproduct pinB−O−Bpin. The use of a copper(I) alkoxide precatalyst and stoichiometric diboron reagent results in catalytic reduction of CO2, with high turnover numbers (1000 per Cu) and frequencies (100 per Cu in 1 h) depending on supporting ligand and reaction conditions

Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds Catalyzed by a Copper Carbene Complex

An N-heterocyclic carbene copper chloride (NHC−CuCl) complex (2) has been prepared and used to catalyze the conjugate reduction of α,β-unsaturated carbonyl compounds. The combination of catalytic amounts of 2 and NaOt-Bu with poly(methylhydrosiloxane) (PMHS) as the stoichiometric reductant generates an active catalyst for the 1,4-reduction of tri- and tetrasubstituted α,β-unsaturated esters and cyclic enones. The active catalytic species can also be generated in situ from 1,3-bis(2,6-di-isopropylphenyl)-imidazolium chloride (1) CuCl2·2H2O in the presence of NaOt-Bu and PMHS

Efficient Homogeneous Catalysis in the Reduction of CO₂ to CO

The well-defined copper(I) boryl complex [(IPr)Cu(Bpin)] [where IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, and pin = pinacolate:  2,3-dimethyl-2,3-butanediolate] deoxygenates CO2 rapidly and quantitatively, affording CO and the borate complex [(IPr)Cu(OBpin)]. The boryl may be regenerated by treatment with the diboron compound pinB−Bpin, giving the stable byproduct pinB−O−Bpin. The use of a copper(I) alkoxide precatalyst and stoichiometric diboron reagent results in catalytic reduction of CO2, with high turnover numbers (1000 per Cu) and frequencies (100 per Cu in 1 h) depending on supporting ligand and reaction conditions

Synthesis, Structure, and Alkyne Reactivity of a Dimeric (Carbene)copper(I) Hydride

The monomeric, two-coordinate carbene complex (IPr)CuO-t-Bu (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) reacts readily with silanes such as triethoxysilane, forming a dimeric copper(I) hydride complex (2) with a very short copper−copper distance. Hydrocupration of 3-hexyne by 2 affords a monomeric copper(I) vinyl complex

Synthesis, Structure, and Alkyne Reactivity of a Dimeric (Carbene)copper(I) Hydride

The monomeric, two-coordinate carbene complex (IPr)CuO-t-Bu (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) reacts readily with silanes such as triethoxysilane, forming a dimeric copper(I) hydride complex (2) with a very short copper−copper distance. Hydrocupration of 3-hexyne by 2 affords a monomeric copper(I) vinyl complex

Catalytic Diboration of Aldehydes via Insertion into the Copper−Boron Bond

Mesitaldehyde reacts cleanly with (IPr)CuB(pin) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene); pin = 2,3-dimethyl-2,3-butanediolate] to afford the product complex 1, the first well-defined product of carbonyl group insertion into a metal−boron bond. Analysis of 1 by NMR spectroscopy and single-crystal X-ray diffraction indicates the formation of a copper−carbon and a boron−oxygen bond. A copper(I) precatalyst supported by the less sterically demanding ligand ICy (1,3-dicyclohexylimidazol-2-ylidene) achieves the efficient 1,2-diboration of aryl-, heteroaryl-, and alkyl-substituted aldehydes at room temperature

A General Synthesis of End-Functionalized Oligoanilines via Palladium-Catalyzed Amination

A General Synthesis of End-Functionalized Oligoanilines via Palladium-Catalyzed Aminatio

Palladium-Catalyzed Synthesis of Monodisperse, Controlled-Length, and Functionalized Oligoanilines

The palladium-catalyzed amination of aryl halides, in conjunction with an orthogonal protective group scheme, forms the basis of two routes to oligoaniline precursors. One method consists of a bidirectional chain growth from a symmetric core piece, whereas the other involves a divergent−convergent synthesis of nonsymmetric fragments, followed by coupling to a symmetric core fragment. The oligoaniline precursors are soluble in a variety of common organic solvents and are easily converted to the deprotected oligoanilines. The method allows the preparation of even or odd chain lengths and the incorporation of a variety of functional groups. The synthesis of phenyl-capped heptaaniline through decaaniline, of four end-functionalized octaaniline derivatives, and of phenyl-capped 16-mer and 24-mer is described. The effects of chain length and substitution upon oligomer behavior have been investigated by electronic absorption spectroscopy and cyclic voltammetry

Copper(I) β-Boroalkyls from Alkene Insertion: Isolation and Rearrangement

The insertion of alkenes into an (NHC)copper(I) boryl affords isolable β-boroalkyl complexes in high yields; competition experiments using substituted styrenes show that electron-donating substituents slow the reaction. Although the insertion products are stable at ambient temperature, a β-hydride elimination/reinsertion sequence affords a rearranged α-boroalkyl complex on heating