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We herein report a nickel-catalyzed migratory cycloisomerization of o-alkynylanilides, giving 2,3-disubstituted indoles in good yields. The cyclization proceeded via acyl transfer on the nitrogen atom of the substrate to C3-position in the product, and an N-heterocyclic carbene (NHC) ligand such as ICy or SICy was found to be suitable in this reaction. It was thought that the reaction proceeds via an aza-nickelcyclepentene intermediate formed from alkyne and the C=O bond of the amide moiety in o-alkynylanilides.

We describe the nickel-catalyzed hydrocarboxylation of ynamides with CO2 and H2O to afford a variety of alpha-amino-alpha, beta-unsaturated esters with high regioselectivities. The selective alpha-carboxylation of ynamides with this catalytic protocol is unexpected in view of the electronic bias of ynamides and is in sharp contrast to our previous study in which a stoichiometric amount of Ni(0) was used to form a beta-carboxylated product exclusively. We revealed that this unexpected C-C bond formation was induced by the combination of Zn and MgBr2.

Doi R., Kajiwara K., Negoro T., et al. Regioselective C-F Bond Transformations of Silyl Difluoroenolates. Organic Letters 25, 5542 (2023); https://doi.org/10.1021/acs.orglett.3c02057., Herein, we report the development of a nickel-catalyzed cross-coupling reaction of silyl difluoroenolates with aryl zinc reagents via C-F bond cleavage. Treatment of a stoichiometric amount of Ni(0)/N-heterocyclic carbene (NHC) with silyl difluoroenolates in the presence of a lithium salt resulted in C-F bond cleavage to selectively afford the corresponding (Z)-alkenyl Ni complexes. On the basis of the observations, we developed a catalytic cross-coupling reaction that selectively delivers a single geometric isomer of a fluoroenolate.

Zhou Y., Doi R., Ogoshi S.. Difluoromethylene insertion into fluoroalkyl copper complexes. Chemical Communications 59, 11504 (2023); https://doi.org/10.1039/d3cc03481j., Herein, we report the insertion of a difluoromethylene into 1,1,2,2-tetrafluoro-2-arylethyl copper complexes to synthesize extended perfluoroalkyl-bridged compounds that have various functional groups on each edge (ArCF2CF2(CF2)nR, R = arenes, halogens, alkyl, alkenyl, and benzyloxycarbonyl). Further, the one-pot syntheses of perfluoroalkyl-bridged compounds from aryl boronic acid esters were carried out.

Zhou Y., Doi R., Ogoshi S.. Difluoromethylene insertion into fluoroalkyl copper complexes. Chemical Communications 59, 11504 (2023); https://doi.org/10.1039/d3cc03481j., Herein, we report the insertion of a difluoromethylene into 1,1,2,2-tetrafluoro-2-arylethyl copper complexes to synthesize extended perfluoroalkyl-bridged compounds that have various functional groups on each edge (ArCF2CF2(CF2)nR, R = arenes, halogens, alkyl, alkenyl, and benzyloxycarbonyl). Further, the one-pot syntheses of perfluoroalkyl-bridged compounds from aryl boronic acid esters were carried out.

Doi R., Kajiwara K., Negoro T., et al. Regioselective C-F Bond Transformations of Silyl Difluoroenolates. Organic Letters 25, 5542 (2023); https://doi.org/10.1021/acs.orglett.3c02057., Herein, we report the development of a nickel-catalyzed cross-coupling reaction of silyl difluoroenolates with aryl zinc reagents via C-F bond cleavage. Treatment of a stoichiometric amount of Ni(0)/N-heterocyclic carbene (NHC) with silyl difluoroenolates in the presence of a lithium salt resulted in C-F bond cleavage to selectively afford the corresponding (Z)-alkenyl Ni complexes. On the basis of the observations, we developed a catalytic cross-coupling reaction that selectively delivers a single geometric isomer of a fluoroenolate.

Doi R., Ogoshi S.. Chemical Strategies for the Cleavage of the C(sp3)−F Bonds in Perfluoroalkyl Groups. European Journal of Organic Chemistry 27, e202301229 (2024); https://doi.org/10.1002/ejoc.202301229., Perfluoroalkyl substances (PFAS) have been recognized as environmental pollutants. Hence, their efficient and mild destruction is a significant research interest. While many research articles and review papers have reported the cleavage of the C(sp2)−F bonds, single C(sp3)−F bond, and CF3 groups in PFAS, in this study, limited and emerging examples of a longer perfluoroalkyl group containing at least one repeating unit of 1,1,2,2-tetrafluoroethylene was focused. In this Concept, we summarized recent progress on the chemical defluorination of PFAS via the cleavage of unactivated C(sp3)−F bonds in longer perfluoroalkyl groups under mild conditions (~150 °C). In addition to classical reductive defluorination, strategies featuring Lewis acid activation and the transient generation of an unsaturated bond were described.

Doi R., Ogoshi S.. Chemical Strategies for the Cleavage of the C(sp3)−F Bonds in Perfluoroalkyl Groups. European Journal of Organic Chemistry 27, e202301229 (2024); https://doi.org/10.1002/ejoc.202301229., Perfluoroalkyl substances (PFAS) have been recognized as environmental pollutants. Hence, their efficient and mild destruction is a significant research interest. While many research articles and review papers have reported the cleavage of the C(sp2)−F bonds, single C(sp3)−F bond, and CF3 groups in PFAS, in this study, limited and emerging examples of a longer perfluoroalkyl group containing at least one repeating unit of 1,1,2,2-tetrafluoroethylene was focused. In this Concept, we summarized recent progress on the chemical defluorination of PFAS via the cleavage of unactivated C(sp3)−F bonds in longer perfluoroalkyl groups under mild conditions (~150 °C). In addition to classical reductive defluorination, strategies featuring Lewis acid activation and the transient generation of an unsaturated bond were described.