Jun-Ichi Asakura

Effect of Solvent on the Radical Copolymerizability of Styrene with Acrylonitrile

Abstract Radical copolymerization of styrene (St, M1) with acrylonitrile (AN, M2) has been carried out using azobisisobutylonitrile as an initiator in benzene, dimethylsulfoxide, acetonitrile, and ethanol at 60 and 80°C. Good linear correlationships were obtained by plotting the values of log r1, log r2, Q2, and e2 against those of vC[dbnd]N and vC[dbnd]C determined in the solvents: the increase in the interaction between AN and the solvent was found to decrease the values of log r1 and e2 but to increase those of log r2 and Q2. The results are discussed in terms of the solvation both in the ground state and in the transition state.

Clay Catalyzed Acetonation: A Simple Method for the Preparation of Isopropylidene Carbohydrates

Abstract This paper reports a simple method for the preparation of isopropylidene carbohydrates using clay as a catalyst. Treatment of various monosaccharides and/or ribonucleosides with acetone in the presence of clay such as a montmorillonite K 10 (K 10) under mild reaction conditions gave isopropylidene carbohydrates (1–7) in good yields.

Free Radical Copolymerization of Styrene with N-Substituted Maleimides in Chiral Substances

Abstract Optically active copolymers were obtained by radical copolymerization of styrene with N-methyl-, N-cyclohexyl- and N-t-butyl-maleimides in l-menthol or N-p-toluenesulfonyl- and N-carbobenzoyloxy-L-prolines.

Cationic Polymerization of N-Vinylcarbazole in the Presence of (+)-D-Camphor-10-sulfonic Acid

Abstract Optical rotation values of the polymers of N-vinylcarbazole (VCZ) obtained by a (+)-D-camphor-10-sulfonic acid (DCS) catalyst were found to increase linearly with an increase in the donor numbers of such solvents as 1,2-dichloroethane, dioxane, and tetrahydro-furan and such additives as N,N-dimethylformamide and tetra-methylurea. Asymmetric induction is considered to be caused by a stereoselective fixation of the growing VCZ cation with the optically active DCS anion, and fixation is assisted by nucleophilic solvation. No optically active VCZ polymer was obtained by using p-toluenesulfonic acid as the catalyst and (2s)-N,N′-carbonyl-N-cyclohexyl-aminomethyl pyrolizine as the additive.

A Mild Procedure for O-Deacylation of the Fully Acylated Sugar Moiety of Nucleosides in the Presence of Cyanide

Abstract The solvolytic O-deacylation of the fully acylated sugar moiety of uridine and thymidine was found to take place readily in the presence of KCN in methanol at room temperature.

Asymmetric Induction in the Free Radical Co polymerization of Isobutyl Vinyl Ether with Maleic Anhydride in l-Menthol

Abstract The radical co polymerization of isobutyl vinyl ether with maleic anhydride was carried out in the presence of l-menthol by using azobisisobutylonitrile. The resulting copolymer was found to be alternating and optically active. The overall activation energy for co polymerization was calculated to be 22.8 kcal/mol in the presence of l-menthol and 22.0 kcal/mol in the absence of l-menthol. The specific rotation of the copolymer decreased with an increase of the reaction temperature.

Photopolymerization of β-Allyloxypropionaldehyde

Abstract Homo- and copolymerizations of β-allyloxypropionaldehyde (I) have been carried out by photoirradiation at 12–13°C in degassed glass ampules. The number-average molecular weights of the homopolymers of I obtained in a few reaction conditions were determined by means of gel-permeation chromatography. I initiated and/or accelerated the photopolymerizations of such vinyl monomers as methyl methacrylate and vinyl acetate. Photocopolymerizabilities of I with styrene (St) and acrylonitrile (AN) were also investigated, and the copolymerization parameters were obtained as follows: for the St-I system, r1 = 12, r2 = 0.01; for the AN-I system, r1 = 5.2, r2 = 0.01.

Radical Copolymerization of Vinylidene Chloride with 3(2-Methyl)-6-methylpyridazinone in Several Solvents

Abstract The radical copolymerization of vinylidene chloride (Vc, M1) with 3(2-methyl)-6-methylpyridazinone (I, M2) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r1 against those of V C[dbnd]O and V C[dbnd]C of monomers determined in the solvents.

Metal Carbonate-Mediated Complete Deacylation of Polyacyl Protected Nucleosides

Abstract Treatment of poly-acetyl or -benzoyl protected ribonucleosides (1a-i) and 2′-deoxyribonucleosides (3a-d) with metal carbonates such as NaHCO3 or Na2CO3 in MeOH gave the corresponding deacylated free ribomucleosides (2a-d and 4a-b) in excellent high yields.

Solvent Effect on the Radical Copolymerizability of Styrene with p-Substituted Methyl Cinnamates

Abstract The radical co polymerization of styrene with p-substituted methyl cinnamates was carried out in benzene, acetonitrile, and acetic acid at 60 and 80°C. The p values obtained by plotting the values of log 1/r1 against a values with the modified Hammetts equation decreased in the order benzene, acetonitrile, and acetic acid. The activation energy and entropy in copolymerization were also estimated. The results are discussed in terms of the different degrees of solvation between the ground state and the transition state.