Copper Catalysis for Synthesizing Main-Group Organometallics Containing B, Sn or Si

A copper complex has proven to be a potent catalyst for forming a C–B bond via diborylation of arynes and alkynes, affording vic-diborylarenes and vic-diborylalkenes with high efficiency. A boryl-substituted organocopper species, which is intermediately generated in the diborylation, has been found to be captured by a tin or a carbon electrophile, leading to threecomponent borylstannylation or carboboration, in which C–B and C–Sn (or C) bonds are constructed simultaneously. Furthermore, reducing the Lewis acidity of the boron center with 1,8-diaminonaphthalene decisively alters the regiochemical behavior of the borylcopper species, enabling the installation of a boryl moiety to occur at an internal carbon of terminal alkynes in borylstannylation and protoboration. Copper catalysis for C–Sn and C–Si bond-forming processes via distannylation, hydrostannylation and silylstannylation, as well as silver catalysis for a C–B bond-forming reaction, is also described.This work was financially supported by Research for Promoting Technological Seeds from the Japan Science and Technology Agency (JST), the Electric Technology Research Foundation of Chugoku, The Mazda Foundation, the Furukawa Technology Promotion Foundation, and the SEI Group CSR Foundation

Borylation of Alkynes under Base/Coinage Metal Catalysis: Some Recent Developments

Alkenylboranes have been vital reagents in modern synthetic organic chemistry, whose carbon–boron bond is transformable into a carbon–carbon bond stereoretentively to give such invaluable mutisubstituted alkenes as natural products, biologically active molecules and functional materials. Introduction of a boryl moiety across a carbon–carbon triple bond of alkynes (borylation of alkynes) is one of the most direct and potent methods for synthesizing alkenylboranes, and this field has thus far experienced remarkable progress mainly with group 10 transition metal catalysts (Ni, Pd, Pt), which enables highly functionalized alkenylboranes to be constructed stereoselectively. On the other hand, much attention has recently been focused on appealing catalysis of base (Fe, Co) and coinage (Cu, Ag, Au) metals toward the borylation of alkynes, which is summarized in this perspective

Copper-catalyzed direct borylation of alkyl, alkenyl and aryl halides with B(dan)

Substitutional borylation of C(sp3 or sp2)–halogen bonds with an unsymmetrical diboron [(pin)B–B(dan)] was found to proceed smoothly under copper catalysis. A variety of masked alkyl-, alkenyl- and arylboron compounds [R–B(dan)] were straightforwardly accessible with high functional group compatibility in high yield.This work was financially supported by JSPS KAKENHI Grant Number JP16H01031 in Precisely Designed Catalysts with Customized Scaffolding

Copper-Catalyzed Arylstannylation of Arynes in Sequence

Copper-catalyzed arylstannylation of arynes has been developed. This transformation enables variously substituted ortho-stannylbiaryls and teraryls to be constructed straightforwardly. An electron-deficient tin center is the key, and thus the single or dual insertion of arynes into arylstannanes is precisely controllable by simply changing the equivalence of aryne precursors.This work was financially supported by JSPS KAKENHI Grant Number JP17K05864

NHC-catalyzed cleavage of vicinal diketones and triketones followed by insertion of enones and ynones

Thiazolium carbene-catalyzed reactions of 1,2-diketones and 1,2,3-triketones with enones and ynones have been investigated. The diketones gave α,β-double acylation products via unique Breslow intermediates isolable as acid salts, whereas the triketones formed stable adducts with the NHC instead of the coupling products

Kinetic construction of the high-beta anisotropic-pressure equilibrium in the magnetosphere

A theoretical model of the high-beta equilibrium of magnetospheric plasmas was constructed by consistently connecting the (anisotropic pressure) Grad–Shafranov equation and the Vlasov equation. The Grad–Shafranov equation was used to determine the axisymmetric magnetic field for a given magnetization current corresponding to a pressure tensor. Given a magnetic field, we determine the distribution function as a specific equilibrium solution of the Vlasov equation, using which we obtain the pressure tensor. We need to find an appropriate class of the distribution function for these two equations to be satisfied simultaneously. Here, we consider the distribution function that maximizes the entropy on the submanifold specified by the magnetic moment. This is equivalent to the reduction of the canonical Poisson bracket to the noncanonical one having the Casimir corresponding to the magnetic moment. The pressure tensor then becomes a function of the magnetic field (through the cyclotron frequency) and flux function, satisfying the requirement of the Grad–Shafranov equation