Tokiji Kawamura

Selective synthesis of 2,6-naphthalenedicarboxylic acid by use of cyclodextrin as catalyst

Abstract The selective synthesis of 2,6-naphthalenedicarboxylic acid from 2-naphthalenecarboxylic acid with carbon tetrachloride, copper powder, and aqueous alkali was achieved by using of β-cyclodextrin (β-CyD) as a catalyst at 60°C under nitrogen, producing 2,6-naphthalenedicarboxylic acid in 67 mol% yield with 84% selectivity. The one-pot preparation of 2,6-naphthalenedicarboxylic acid from naphthalene was attained at 84°C by using of β-CyD, producing 2,6-naphthalenedicarboxylic acid in 65 mol% yield with 79% selectivity. When α-CyD or γ-CyD was used instead of β-CyD on the carboxylation of 2-naphthalenecarboxylic acid and naphthalene, respectively, the reaction hardly proceeded. The conformation of β-CyD–2-naphthalenecarboxylate inclusion complex in aqueous alkaline solution was determined by the nuclear magnetic resonance spectroscopy using 1 H homonuclear Overhauser enhancement on the rotating frame. The 2-naphthalenecarboxylate anion was axially included in the cavity of β-CyD with an orientation which directed the 5-, 6-, and 7-positions of 2-naphthalenecarboxylate anion to the secondary hydroxyl side of β-CyD. It was concluded that the high selectivity of the carboxylation of 2-naphthalenecarboxylic acid was ascribed to the conformation of the β-CyD–2-naphthalenecarboxylate inclusion complex. The selective carboxylation of naphthalene was attributed to the formations of the β-CyD–naphthalene and β-CyD–2-naphthalenecarboxylate inclusion complexes.

13C-NMR investigations of synthetic branched polysaccharides

Abstract 13C-NMR spectra of glucose-branched polysaccharides synthesized by the reaction of 3,4,6tri-O-acetyl-(1,2-O-ethylortho-acetyl)-α- d -glucopyranose with curdlan or cellulose acetate followed by deacetylation were measured and assigned. Although most of the branches are β-(1 → 6) linked, a small amount of α-(1 → 6)linked branches were found.

The effect of the counter-anion on the steric structure of poly(alkenyl ether)s in cationic polymerization

Ethyl propenyl and butenyl ethers were polymerized in toluene at −78°C by a variety of catalysts, and effect of a counter-anion on steric structure of the polymer was investigated. The trans monomer produced stereoregular polymer with threo-meso structure and its content was independent of kind of the catalysts. In the polymerization of the cis monomer, the contents of the threo-meso and racemic structures of the poly(cis-propenyl ether) depended on the kind of the catalysts whereas those of the poly (cis-butenyl ether) having bulky β-ethyl groups did not. The difference of the counter-anion effect was discussed on the basis of the difference of the β-substituent in bulkiness.