Steric bulk around catalytic centers is one of the most important factors determining catalytic reactivities and selectivities. This paper reports the synthesis of structurally diverse 5-iodo-3-methyl-1,2,3-triazolium salts and the evaluation of their catalytic activities as halogen-bonding donors for the aza-Diels-Alder reaction of 2-siloxy-1,3-butadiene with imines. We found that steric hindrance around an iodide atom in halogen-bonding donors significantly impacted catalytic efficiency.

Cationic halogen-bonding-donors with little or non-coordinating counter anions have attracted great attention as new Lewis acid type organocatalysts. However, these anions cannot function as nucleophilic activation sites due to their...

Nanocomposite hydrogels (NC gels) composed of polymer–clay networks are successfully synthesized via initiator-free (IF) photopolymerization in aqueous media using plasma-treated clay. IF-NC gels with a high tensile strength, strain at break, and thermoresponsiveness, which are almost identical to those of NC gels prepared by redox and photoinitiator methods, are obtained by optimizing the plasma-treatment conditions and exfoliation in water. The clay nanosheets play important roles as initiators, multifunctional cross-linkers, and auxiliary agents for facilitating in situ free-radical polymerization toward IF-NC gels. The mechanism for the formation of the polymer–clay network in the IF-NC gels is clarified through Fourier transform infrared and electron spin resonance studies and involves the formation of hydroperoxides and radicals on the clay surface by plasma treatment and subsequent UV irradiation, respectively, and through designed free-radical polymerization experiments in the presence or absence of the clay nanosheets. Because of their simple and versatile syntheses, form and size diversities, and superb characteristics, IF-NC gels can be used in a variety of applications. The results provide important insight into super-hydrogels and organic–inorganic nanocomposites, as well as polymer synthesis and photochemistry.

We report a fluoride-mediated nucleophilic aromatic amination of chloro-1H-1,2,3-triazolium salts with aliphatic amines. The reaction proceeded under mild reaction conditions to provide amino-1,2,3-triazolium salts with various functional groups, which can be utilized for further transformations. Moreover, it was found that an amino-1,2,3-triazolium salt was transformed via deprotonation into the N-heterocyclic imine (NHI), which exhibited the excellent catalytic activity for the cyanosilylation of acetophenone with trimethylsilyl cyanide.

The first example of palladium-catalyzed direct formylation of arylzinc reagents using S-phenyl thioformate is reported. The reaction proceeded under mild conditions, allowing high functional group tolerance. In addition, the developed formylation method was used to prepare deuterated and C-labeled aryl aldehydes from isotope-labeled S-phenyl thioformates. Moreover, this procedure was applied to an alkenylzinc halide, affording the corresponding enal.