Tris(pentafluorophenyl)borane-Catalyzed Stereospecific Bromocyanation of Styrene Derivatives with Cyanogen Bromide.

We, herein, report on the bromocyanation of styrene derivatives with cyanogen bromide in the presence of tris(pentafluorophenyl)borane which functions as a Lewis acid catalyst that can effectively activate cyanogen bromide. This reaction proceeds through a stereospecific -addition. The protocol is operationally simple and provides practical access to β-bromonitriles.

Anthracene-Attached Persistent Tricyclic Aromatic Hydrocarbon Radicals.

Anthracene-attached tricyclic aromatic hydrocarbon radicals having different central polygons, Ant-5, Ant-6, and Ant-7, were synthesized to evaluate the role of an anthracene substituent group in the stability and reactivity of tricyclic aromatic hydrocarbon radicals. The bulky anthryl group effectively protects a carbon atom with high spin density, resulting in high persistence of the radicals. On the other hand, the combination of the anthryl group and the tricyclic aromatic scaffold makes the molecular structure drastically change from a twisted form to a folded form and an unpaired electron moves into the anthryl moiety, eventually affording a tail-to-tail σ-dimer.

Enantioselective Electrophilic Cyanation of Boron Enolates: Scope and Mechanistic Studies.

Chiral β-ketonitriles bearing a stereogenic carbon center at the α-position are an important class of compounds, many of which serve as useful synthetic intermediates for the preparation of chiral 1,3-aminoalcohols, β-hydroxy nitriles, and related derivatives. Although the enantioselective electrophilic cyanation of enolate equivalents is one of the most promising approaches for the synthesis of chiral β-ketonitriles, the available methods are largely limited to reactions of 1,3-dicarbonyl compounds. Herein, we report on enantioselective electrophilic cyanation of boron enolates, which are readily prepared from α,β-unsaturated ketones and diisopinocampheylborane (Ipc BH) to afford chiral β-ketonitriles with a high level of enantioselectivity.

Catalytic Activation of 1-Cyano-3,3-dimethyl-3-(1H)-1,2-benziodoxole with B(CF) Enabling the Electrophilic Cyanation of Silyl Enol Ethers.

The Lewis acidic activation of a hypervalent iodine reagent containing a transferable cyano group, 1-cyano-3,3-dimethyl-3-(1H)-1,2-benziodoxole (CDBX), with B(CF), to achieve the catalytic electrophilic cyanation of silyl enol ethers is presented. Mechanistic studies indicate that CDBX is activated through coordination of its cyano group to B(CF), thus enabling the electrophilic cyanation reaction to occur.

Electrophilic Cyanation of Boron Enolates: Efficient Access to Various β-Ketonitrile Derivatives.

The highly efficient electrophilic cyanation of boron enolates using readily available cyanating reagents, N-cyano-N-phenyl-p-toluenesulfonamide (NCTS) and p-toluenesulfonyl cyanide (TsCN), is reported. Various β-ketonitriles were prepared by this new protocol, which has a remarkably broad substrate scope compared to existing methods. The present method also allowed efficient synthesis of β-ketonitriles containing a quaternary α-carbon center.

Straightforward synthesis of 1,2-dicyanoalkanes from nitroalkenes and silyl cyanide mediated by tetrabutylammonium fluoride.

A straightforward synthesis of 1,2-dicyanoalkanes by reacting nitroalkenes with trimethylsilyl cyanide in the presence of tetrabutylammonium fluoride is described. The reaction proceeds through a tandem double Michael addition under mild conditions. Employing the hypervalent silicate generated from trimethylsilyl cyanide and tetrabutylammonium fluoride is essential for achieving this transformation.