Controlled release of the guest molecule via borate formation of a fluorinated boronic ester cage.

A boronic ester cage, which exhibits stimuli-responsive guest-release behavior, was constructed by self-assembly of tetrol with the indacene backbone and a fluorine-substituted benzenetriboronic acid derivative. The presence of fluorine substituents made it possible to control the guest release rate using simple amines by forming tetrahedral borates.

Release and recovery of guest molecules during the reversible borate gel formation of guest-included macrocyclic boronic esters.

Borate gel formation from guest-encapsulated macrocyclic boronic esters was realized by the addition of a diamine to the suspension of the boronic esters in various organic solvents, which triggered the release of the guest compounds. The guest molecules could be recovered from the borate gel by addition of an acid to remove the diamine, which facilitated the reconstruction of the initial guest-encapsulated macrocyclic boronic esters.

Rhenium- and manganese-catalyzed synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes.

We have succeeded in the development of three approaches to the synthesis of aromatic compounds from 1,3-dicarbonyl compounds and alkynes. The first approach is a manganese-catalyzed [2+2+2] cycloaddition between 1,3-dicarbonyl compounds, which have no substituents at the active methylene moiety, and terminal alkynes. This reaction proceeds with high regioselectivity when aryl acetylenes are employed as the alkyne component.

Rhenium- and manganese-catalyzed insertion of acetylenes into beta-keto esters: synthesis of 2-pyranones.

Rhenium- and manganese-catalyzed reactions between beta-keto esters and acetylenes, followed by treatment with tetrabutylammonium fluoride, gave 2-pyranone derivatives regioselectively.

Rhenium-catalyzed synthesis of multisubstituted aromatic compounds via C-C single-bond cleavage.

A reaction between a beta-keto ester and an acetylene in the presence of a rhenium complex, [ReBr(CO)3(thf)]2, as a catalyst, provided a 2-pyranone derivative in excellent yield via retro-aldol reaction (C-C single bond cleavage). By adding an acetylene-bearing ester group(s) after the formation of 2-pyranones, an aromatization reaction proceeded and multisubstituted aromatic compounds were obtained in good to excellent yields.