Shizuo Fujisaki

Convenient selective monoesterification of α, ω-dicarboxylic acids catalyzed by ion-exchange resins

Abstract Symmetric dicarboxylic acids, ranging from pentanedioic acid to tetradecanedioic acid, gave selectively the corresponding monoesters in high yields in the transesterification catalyzed by strongly acidic ion-exchange resins in ester/octane mixtures.

An effective chlorinating agent benzyltrimethylammonium tetrachloroiodate, benzylic chlorination of alkylaromatic compounds☆

Abstract The reaction of alkylaromatic compounds with benzyltrimethylammonium tetrachloroiodate in carbon tetrachloride in the presence of AIBN under reflux for several hours gave α-chloro-substituted compounds in fairly good yields.

Selective monoesterification of dicarboxylic acids catalysed by ion-exchange resins

Symmetrical dicarboxylic acids with 4–14 carbon atoms gave selectively the corresponding monoesters in high yields in the transesterification catalysed by strongly acidic ion-exchange resins in ester–hydrocarbon mixtures. It was found that the rate of the esterification of the dicarboxylic acids is much higher than that of the monocarboxylic acids formed. This result can explain the high selectivity for the monoester formation and can also be explained by the existence of an aqueous layer on the surface of the resins. This method of selective esterification is quite simple and practical.

Halogenation using quaternary ammonium polyhalides. Part 22. Selective bromination of aromatic ethers with benzyltrimethylammonium tribromide

The reaction of aromatic ethers with a stoicheiometric amount of benzyltrimethylammonium tribromide in dichloromethane–methanol or acetic acid–ZnCl2 under mild conditions gave, selectively, mono-, di-, or tri-bromo-substituted aromatic ethers in quantitative yields.

Regioselective bromination of phenols

Abstract Regioselective bromination of phenols gave 2-bromo-, 4-bromo-, 2,6-dibromo-2,4-dibromo, 2-bromo-6-substituted, 4-bromo-2-substituted and 2,4-dibromo-6-substituted phenols, respectively. Especially, 2-bromo-, 2,6-dibromo- and 2-bromo-6-substituted phenols which were prepared via long steps, were obtained in NBS-amine (primary and secondary) system in high yields under ordinary conditions. The scope and their mechanisms were discussed.

An exploration of the binding site of aldolase using N-(ω-hydroxyalkyl)glycolamidobisphosphoric esters

N-(omega-Hydroxyalkyl)glycolamidobisphosphoric esters (P-O-CH2-CO-NH-(CH2)n -O-P), which are analogues of the aldolase (D-fructose-1,6-bisphosphate D-glyceraldehyde-3-phosphate-lyase, EC 4.1.2.13) substrate fructose 1,6-bisphosphate, were synthesized and used for probing its active site. These phosphate compounds competitively inhibited aldolase activity. The Ki value was lowest when the maximum distance between the phosphorus atoms of the bisphosphate was brought close to that of fructose 1,6-bisphosphate. The inhibitor constants, Ki, were compared to those of alkanediol monoglycolate bisphosphoric esters and alkanediol bisphosphate compounds, which were reported previously by Ogata et al. The values of Ki for the bisphosphate compounds containing an amide group, the amide bisphosphate compounds, were smaller than those for the bisphosphate compounds containing an ester group, the ester bisphosphate compounds, and those for alkanediol bisphosphates were the largest for the same distance between phosphorus atoms in these bisphosphates. The difference spectra of aldolase caused by binding of a saturating concentration of N-(omega-hydroxypropyl)glycolamidobisphosphoric ester resembled that of butanediol monoglycolate bisphosphoric ester. However, the effects of the amide bisphosphate compounds on the absorption spectrum of aldolase were smaller than those of the ester bisphosphate compounds for the same distance between phosphorus atoms in these bisphosphate compounds. These results suggest that the synthesized phosphate compounds bind to aldolase at the active site and the -CO-NH- group of the compounds might be held more tightly than the -CO-O- group by hydrogen bonds, presumably with the amino acid residues in the active site, such as Lys-146 or -229 and Asp-33 or Glu-187. On the other hand, the -CO-O- group might be more effective in changing the environment of the Trp-147 residue in the active site of this enzyme.

Facile synthesis of N-bromoamides using benzyltrimethylammonium tribromide in alkaline solution

Aliphatic and aromatic amides reacted with a stoicheiometric amount of benzyltrimethylammonium tribromide in ice-cold aqueous sodium hydroxide to give N-bromoamides in good yields.

Highly selective monotetrahydropyranylation of symmetrical diols catalysed by a strongly acidic ion-exchange resin

Several primary and secondary symmetrical diols, ranging from propane-1,3-diol to decane-1,10-diol, are selectively monoprotected by monotetrahydropyranyl ether formation catalysed by a strongly acidic ion-exchange resin (Dowex 50w × 2, 50–100 mesh) in a 3,4-dihydro-2H-pyran-hydrocarbon mixture.

Conversion of ketals to ketones by nitrogen dioxide in the presence of silica gel

Nitrogen dioxide transforms ketals to ketones in the presence of silica gel under neutral, anhydrous and mild conditions.