Visible-Light-Driven C-H Imidation of Arenes and Heteroarenes by a Phosphonium Ylide Organophotoredox Catalyst: Application to C-H Functionalization of Alkenes.

Phosphonium ylide catalysis through an oxidative quenching cycle has been developed for visible-light-driven C-H imidation of arenes and heteroarenes. The present protocol could be applied not only to trihalomethylative lactonization reactions involving trifluoromethyl, trichloromethyl, and tribromomethyl radicals but also to the first example of an organophotoredox-catalyzed imidative lactonization reaction involving a nitrogen-centered electrophilic radical species.

Ring-fused hexahydro-1,2,4,5-tetrazines: synthesis, structure, and mechanistic studies on isolable rotational isomers.

We designed conformationally stable rotational isomers around the C(sp2)-C(sp3) axis at the C3-position of hexahydro-1,2,4,5-tetrazines. Isolation of each rotamer by silica gel column chromatography was successfully achieved at room temperature. The proposed isomerization mechanism of the rotamers was supported by NMR kinetic studies.

Tetraarylphosphonium salt-catalyzed formal [3+2] cycloaddition between epoxides and trichloroacetonitrile for the synthesis of ß-amino alcohol derivatives.

Efficient regioselective synthesis of ß-amino alcohol derivatives, including enantioenriched ones, by a tetraarylphosphonium salt-catalyzed coupling reaction of epoxides with trichloroacetonitrile is described. Formal [3+2] cycloaddition, followed by hydrolysis, proceeded smoothly to afford N-protected ß-amino alcohols in good yields.

Asymmetric Cycloadditions of Acyclic Carbonyl Ylides with Aldehydes Catalyzed by a Chiral Binaphthyldiimine-Ni(II) Complex: Enantioselective Synthesis of 1,3-Dioxolanes and Mechanistic Studies by DFT Calculations.

Chiral binaphthyldiimine-Ni(II)-catalyzed asymmetric 1,3-dipolar cycloaddition reactions between acyclic carbonyl ylides generated from donor-acceptor oxiranes and aldehydes are reported. Both aromatic and aliphatic aldehydes could be used as dipolarophiles, providing cis-1,3-dioxolanes with high diastereo- and enantioselectivities. On the basis of mechanistic studies, a monomeric chiral Ni(II) complex was hypothesized to act as the active species for the cycloaddition. The high levels of asymmetric induction are satisfactorily explained by a concerted-asynchronous endo Si-face approach of the aldehyde.

Switchable synthesis of cyclic carbamates by carbon dioxide fixation at atmospheric pressure.

The base-promoted switchable synthesis of five- and six-membered cyclic carbamates using atmospheric pressure carbon dioxide as the C1 source was developed. The chemoselectivity of products was simply controlled by changing bases and solvents. The reaction proceeds effectively under mild conditions, affording valuable cyclic carbamates. Experimental results and DFT studies revealed the reaction mechanism.

Chiroptical switching caused by crystalline/liquid crystalline phase transition of a chiral bowl-shaped molecule.

The liquid crystal of a chiral bowl-shaped molecule having a central-phosphorus atom and long alkyl chains was developed. The DSC and XRD analyses suggested the formation of columnar liquid crystals of both the enantiopure and racemic compounds. The condensed phase of the enantiopure compound in a thin film exhibited a significant signal in CD spectra, which was switched by a reversible phase transition between the crystalline and liquid crystalline states.

Tuning the depth of bowl-shaped phosphine hosts: capsule and pseudo-cage architectures in host-guest complexes with C60 fullerene.

Bowl-shaped phosphine molecules, whose bowl geometry can be controlled by a variation of the axial substituent, were synthesized, and used as host molecules to encapsulate C60. Host molecules with relatively shallow bowls formed a chiral capsule, while hosts with deeper bowls formed an achiral pseudo-cage.