Facile Sc(OTf)₃-Catalyzed Generation and Successive Aromatization of Isobenzofuran from <i>o</i>-Dicarbonylbenzenes

Isobenzofuran can be prepared from o-phthalaldehyde using hydrosilane. The formed isobenzofuran is trapped by an alkene via a Diels–Alder reaction. Further dehydration proceeds to furnish the conjugated aromatic compound. This multistep reaction was promoted by catalytic amounts of Sc(OTf)3

Sequential Ruthenium-Catalyzed Hydroamination and Rhenium-Catalyzed C−H Bond Activation Leading to Indene Derivatives

Formal [3+2] annulation of arylacetylenes and α,β-unsaturated carbonyl compounds is achieved in a one-pot reaction by successive treatment of the acetylenes with aniline and a catalytic amount of Ru3(CO)12 and NH4PF6 and C−H bond activation catalyzed by [ReBr(CO)3(thf)]2. The result suggests that the second rhenium-catalyzed indene formation is not disturbed by the first catalyst system

Countercation Engineering of Graphene-Oxide Nanosheets for Imparting a Thermoresponsive Ability

Graphene-oxide (GO) nanosheets, which are oxidized derivatives of graphene, are regarded as promising building blocks for functional soft materials. Especially, thermoresponsive GO nanosheets have been widely employed to develop smart membranes/surfaces, hydrogel actuators, recyclable systems, and biomedical applications. However, current synthetic strategies to generate such thermoresponsive GO nanosheets have exclusively relied on the covalent or non-covalent modification of their surfaces with thermoresponsive polymers, such as poly(N-isopropylacrylamide). To impart a thermoresponsive ability to GO nanosheets themselves, we focused on the countercations of the carboxy and acidic hydroxy groups on the GO nanosheets. In this study, we established a general and reliable method to synthesize GO nanosheets with target countercations and systematically investigated their effects on thermoresponsive behaviors of GO nanosheets. As a result, we discovered that GO nanosheets with Bu4N+ countercations became thermoresponsive in water without the use of any thermoresponsive polymers, inducing a reversible sol–gel transition via their self-assembly and disassembly processes. Owing to the sol–gel transition capability, the resultant dispersion can be used as a direct writing ink for constructing a three-dimensionally designable gel architecture of the GO nanosheets. Our concept of “countercation engineering” can become a new strategy for imparting a stimuli-responsive ability to various charged nanomaterials for the development of next-generation smart materials

Synthesis of Visible-Light-Responsive Nanocarbon and Application for Photocatalytic Carbon–Carbon Bond Formation

Visible-light-responsive nanocarbon was systematically synthesized via a one-step hydrothermal method, using citric acid and Congo Red; this nanocarbon exhibited visible-light absorption at 516 nm and photocatalytic activity for the carbon–carbon bond-forming reaction between benzylamine and ethyl cyanoacetate. Mechanistic investigations proved that this system generates radicals and the reactions proceed via radical pathways, which are confirmed by electron spin resonance. A metal-free, mildly conditioned, and recyclable photocatalytic reaction was achieved by the visible-light-responsive nanocarbon system

In Situ Synthesis of Ultrathin Amorphous Silica Nanosheet with Large Specific Surface Area on Graphene Oxide

Controlling the assembly of silica, forming monolith, mesoporous, dendritic, and nanosheet structures, has been conducted using a template method with an appropriate solvent or surfactant. Recently, two-dimensional materials, such as graphene oxide (GO), were used as the template to fabricate silica nanosheets (SNs). SNs with a lamellar structure and unique properties have been synthesized using surfactant as the template; however, SNs with ultrathin thicknesses below 2 nm and high specific surface areas have not been achieved previously. Therefore, we developed the in situ synthesis of ultrathin SNs using GO functionalized with alkoxysilanes that have amino groups. The SNs were about 1 nm thick and had an amorphous structure and high specific surface areas (904 m2/g)

Rhenium-Catalyzed Insertion of Aldehyde into a C−H Bond: Synthesis of Isobenzofuran Derivatives

A rhenium complex, [ReBr(CO)3(thf)]2, catalyzed reactions of aromatic ketimines with aldehydes to give isobenzofuran derivatives in good to excellent yields. In contrast to ruthenium and rhodium catalysts, aldehydes, which are polar unsaturated molecules, inserted into the C−H bond after activation by the rhenium complex

Synthesis of Cp−Re Complexes via Olefinic C−H Activation and Successive Formation of Cyclopentadienes

Synthesis of Cp−Re Complexes via Olefinic C−H Activation and Successive Formation of Cyclopentadiene