Sensuke Ogoshi

Intramolecular Arylcyanation of Alkenes Catalyzed by Nickel/AlMe2Cl

A catalyst system derived from nickel and cocatalytic AlMe2Cl effects the intramolecular arylcyanation of alkenes. The reaction takes place in an exclusive exo-dig manner to give a wide range of nitriles having a benzylic quaternary carbon in good yields. Detailed investigations are described on the scope and mechanism as well as preliminary results on the asymmetric version of the reaction to provide novel access to chiral quaternary stereocenters.

Nickel/Lewis acid-catalyzed cyanoesterification and cyanocarbamoylation of alkynes.

Cyanoformates and cyanoformamides are found to add across alkynes by nickel/Lewis acid (LA) cooperative catalysis to give beta-cyano-substituted acrylates and acrylamides, respectively, in highly stereoselective and regioselective manners. The resulting adducts serve as versatile synthetic building blocks through chemoselective transformations of the ester, amide, and cyano groups as demonstrated by the synthesis of typical structures of beta-cyano ester, beta-amino nitrile, gamma-lactam, disubstituted maleic anhydride, and gamma-aminobutyric acid. The related reactions of cyanoformate thioester and benzoyl cyanide, on the other hand, are found to add across alkynes with decarbonylation in the presence of a palladium/LA catalyst.

Palladium-Catalyzed Coupling Reactions of Tetrafluoroethylene with Arylzinc Compounds

Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields.

Nickel-Catalyzed Dehydrogenative [4 + 2] Cycloaddition of 1,3-Dienes with Nitriles

Pyridines, which comprise one of the most important classes of the six-membered heterocyclic compounds, are widely distributed in nature, and the transition-metal-catalyzed [2 + 2 + 2] cycloaddition reaction of two alkynes and a nitrile is one of the most powerful methods for preparing versatile, highly substituted pyridine derivatives. However, the lack of chemo- and regioselectivity is still a crucial issue associated with fully intermolecular [2 + 2 + 2] cycloaddition. The present study developed the Ni(0)-catalyzed intermolecular dehydrogenative [4 + 2] cycloaddition reaction of 1,3-butadienes with nitriles to give a variety of pyridines regioselectively.

Nickel-Catalyzed Selective Conversion of Two Different Aldehydes to Cross-Coupled Esters

In the presence of a Ni(0)/NHC catalyst, an equimolar mixture of aliphatic and aryl aldehydes can be employed to selectively yield a single cross-coupled ester. This reaction can be applied to a variety of aliphatic (1°, 2°, cyc-2°, and 3°) and aryl aldehyde combinations. The reaction represents 100% atom efficiency and generates no waste. Mechanistic studies have revealed that the striking feature of the reaction is the simultaneous coordination of two aldehydes to Ni(0).

Nickel-catalyzed [2 + 2 + 2] cycloaddition of two enones and an alkyne.

A fully intermolecular [2 + 2 + 2] cycloaddition of two enones and an alkyne has been achieved. This reaction proceeds stereoselectively to give one diastereomer as a sole product.

Hydrofluoroarylation of alkynes with fluoroarenes

A combination of Ni(cod)(2) and PCyp(3) is found to be an effective catalyst for chemoselective activation of the C-H bond of fluoroarenes over C-F bonds followed by insertion of alkynes to allow direct alkenylation of the electron-deficient arenes. The characteristics of the reactions are: a C-H bond ortho to a fluorine substituent is selectively activated; the reactivity of fluorobenzenes is roughly proportional to the number of fluorine atoms. The reaction conditions tolerate a broad range of both alkynes and fluoroarenes containing both electron-withdrawing and -donating groups, thus allowing efficient synthesis of a variety of substituted ethenes containing a fluoroaryl motif in high regio- and stereoselective manners. Mechanistic studies including both labeling experiments and stoichiometric reactions reveal that oxidative addition of C-H bonds in fluoroarenes to nickel(0) is kinetically highly facile whereas that of C-F bonds is thermodynamically favoured.

Nickel-Catalyzed Direct Conjugate Addition of Simple Alkenes to Enones

A direct conjugate addition of simple alkenes to enones has been achieved in the presence of a Ni(0)/PCy(3) catalyst.

Synthesis of five- and six-membered benzocyclic ketones through intramolecular alkene hydroacylation catalyzed by nickel(0)/N-heterocyclic carbenes.

Transition-metal-catalyzed hydroacylation has been accepted as a promising synthetic method to form carbon–carbon bonds between an aldehyde and unsaturated compounds, such as alkenes, alkynes, and ketones. A number of catalyst systems have been developed, and high enatio-, regio-, and chemo-selectivity has been achieved. Despite these extensive efforts and praiseworthy results, an inevitable side reaction persists: decarbonylation from an acyl metal intermediate, which causes a decrease in atom-efficiency and a deactivation of the catalyst through the coordination of carbon monoxide (Scheme 1, path a). Major advances in

Nickel-catalyzed Tishchenko reaction via hetero-nickelacycles by oxidative cyclization of aldehydes with nickel(0) complex

A Ni(0)-catalyzed Tishchenko reaction which can be applied to a variety of aliphatic aldehydes (primary, secondary, tertiary) and aromatic aldehydes was developed. The reaction might proceed via a hetero-nickelacycle intermediate.