Nucleosides and nucleotides. 191 : Ring expansion reaction of 1-[2,3,5-tri-o-TBS-4α-formyl-β-D-ribo-pentofuranosyl]uracil by treating with (methylene)triphenylphosphorane to give a new nucleoside containing dihydrooxepine ring at the sugar moiety

When 1-[2,3,5-tri-O-TBS-4α-formyl-β-D-ribo-pentofuranosyl]uracil (5) was treated with (methylene)triphenylphosphorane in THF, an unusual ring-expansion reaction occurred to give a nucleoside (7) containing dihydrooxepine ring at the sugar moiety. A deuterium-label experiment showed that one carbon unit derived from the ylide was incorporated into the 5'-position of 7. A ring cleavage between the C-3' and C-4' of 5 during the reaction was suggested.     

High-pressure subsonic mode operation of chemical oxygen-iodine laser

A new regime of chemical oxygen-iodine laser (COIL), high-pressure subsonic mode operation, was demonstrated using a jet-type singlet oxygen generator (SOG). The laser output power of 342 W with chemical efficiency of 20.9% was obtained at the Cl₂ flow rate of 18 mmol/s and the operating pressure of 6.4 Torr in the laser cavity. The specific energy was 3.1 J/l which was four times higher than our supersonic device, and was comparable to the highest value for the supersonic regime. The experimental results were in good agreement with the numerical simulation results. Received: 26 February 1999 / Revised version: 13 July 1999 / Published online: 30 November 1999     

Analysis of XPS and XES of diamond and graphite by DFT calculations using model molecules

X‐ray photoelectron and emission spectra (XPS and XES) of diamond and graphite have been analyzed by deMon density‐functional theory (DFT) calculations using the model adamantane derivative (C₁₀H₁₂(CH₃)₄) and pyrene (C₁₆H₁₀) molecules, respectively. The theoretical valence photoelectron and C Kα X‐ray emission spectra for the allotrope are in good accordance with the experimental ones. The combined analysis of the valence XPS and C Kα XES enables us to divide the valence electronic distribution into the individual contributions for pσ‐, and pπ‐bonding MOs of the diamond and graphite, respectively. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 102–108, 2001     

Synthesis of hybrid resins via polysiloxane with methacryloyloxy groups

A polysiloxane derivative with methacryloyloxy groups (MPS) that was obtained from the reaction of polymeric tributylstannyl ester of silicic acid and (3‐methacryloyloxypropyl)dimethylchlorosilane was demonstrated to be a useful inorganic component for the preparation of organic–inorganic hybrid resins as nanocomposites. The copolymerizations of MPS with common monomers such as styrene, acrylonitrile, and methyl methacrylate proceeded readily at room temperature under UV irradiation to give the corresponding resins in good yields. The resins obtained from MPS and methyl methacrylate showed good transparency, hardness in a scratch test, and resistance to toluene but had poor flexibility. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1–7, 2001     

Structural analysis of polyhydroxyurethane obtained by polyaddition of bifunctional five‐membered cyclic carbonate and diamine based on the model reaction

This article focuses on the structural analysis of polyhydroxyurethane obtained by the reaction of 2,2‐bis[p‐(1,3‐dioxolan‐2‐one‐4‐yl‐methoxy)phenyl]propane with a diamine based on the model reaction. The compounds obtained in the model reaction could be separated into hydroxyurethanes containing primary and secondary alcohol groups by preparative gel permeation chromatography with a recycling technique to determine the structures by ¹H NMR, ¹³C NMR, distortionless enhancement by polarization transfer (DEPT) and C H correlation spectroscopy to obtain hydroxyurethane carrying the primary alcohol structure moiety dominantly. The ratios were independent of the reaction temperature but somewhat dependent on the solvents and amines. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 851–859, 2001     

Chemical synthesis of poly‐γ‐glutamic acid by polycondensation of γ‐glutamic acid dimer: Synthesis and reaction of poly‐γ‐glutamic acid methyl ester

α‐Methyl glutamic acid (L ‐L )‐, (L ‐D )‐, (D ‐L )‐, and (D ‐D )‐γ‐dimers were synthesized from L ‐ and D ‐glutamic acids, and the obtained dimers were subjected to polycondensation with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride and 1‐hydroxybenzotriazole hydrate as condensation reagents. Poly‐γ‐glutamic acid (γ‐PGA) methyl ester with the number‐average molecular weights of 5000∼20,000 were obtained by polycondensation in N,N‐dimethylformamide in 44∼91% yields. The polycondensation of (L ‐L )‐ and (D ‐D )‐dimers afforded the polymers with much larger |[α]_D | compared with the corresponding dimers. The polymer could be transformed into γ‐PGA by alkaline hydrolysis or transesterification into α‐benzyl ester followed by hydrogenation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 732–741, 2001     

New Transformation of 1,3‐Oxathiolane‐2‐thione into 1,3‐Dithiolan‐2‐one via Polymerization and Depolymerization

This article deals with the cationic and anionic depolymerization of polydithiocarbonate, which was synthesized by cationic polymerization of 5‐phenoxymethyl‐1,3‐oxathiolane‐2‐thione ( 1 ) using methyl triflate as the initiator. The cationic depolymerization of the obtained polymer was carried out in the presence of 5–20 mol‐% of methyl triflate or triflic acid catalyst in chlorobenzene at 60 °C for 96 h to afford 4‐phenoxymethyl‐1,3‐dithiolan‐2‐one ( 2 ) in 35–83% yield. The anionic depolymerization of the polymer was carried out in the presence of 5 mol‐% of triethylamine or potassium tert‐butoxide at 20 °C for 24 h to afford 2 in 85–100% yield.     

Addition of five‐membered cyclic carbonate with amine and its application to polymer synthesis

A bifunctional five‐membered cyclic carbonate was synthesized from carbon dioxide and diglycidyl terephthalate, and its polyaddition with alkyl diamines were carried out in DMF at room temperature to obtain the corresponding poly(hydroxyurethane)s with M_n s in the range of 6300–13200 in good yields. The structures of the obtained polymers were confirmed by IR and NMR spectroscopy and their glass‐transition and decomposition temperatures were observed at 3–29 °C and 182–277 °C, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2375–2380, 2000     

Structure–initiator activity dependence of aminimides as thermally latent initiators in the polymerization of glycidyl phenyl ether

Novel aliphatic aminimides were synthesized from the corresponding carboxylic acid esters, 1,1‐dimethylhydrazine, and epoxides in 54–95% yields. Bulk polymerization of glycidyl phenyl ether (GPE) with 3 mol % of the aminimides was evaluated by DSC as a model process for curing of epoxy resin. All the aminimides showed no exothermic DSC peak below 120 °C but showed sharp exothermic peaks above 137 °C, indicating good thermal latency. Good relationships were observed between the calculated bond length from the carbonyl carbon to the α‐carbon of the aliphatic group (R C), DSC onset temperatures, and the thermal dissociation temperatures (T_d 's) of the aminimides. The aminimide with a longer R C bond length showed lower T_d and DSC onset temperature, that is, higher activity. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3428–3433, 2000     

Living anionic polymerization of ethylphenylketene: A novel approach to well‐defined polyester synthesis

A living polymerization of ethylphenylketene (EPK) was accomplished. When polymerization of EPK was carried out with butyllithium as an initiator in tetrahydrofuran (THF) at −20 °C, EPK was completely consumed within 5 min, and the corresponding polyester with narrow molecular weight distribution (M_w /M_n ∼ 1.1) was obtained almost quantitatively. Kinetic study of the polymerization at −78 °C revealed that conversion of EPK agreed with the first‐order kinetic equation, and that M_n of the polymer increased in virtually direct proportion to the conversion. Along with these results, successful results in postpolymerization at −20 °C strongly supported living mechanism of the present polymerization. Further, lithium alkoxides having a methoxy group, styryl moiety, and nitroxyl radical, also successfully initiated polymerization of EPK to afford the corresponding polymers having functional initiating ends. In the polymerization with varying feed ratio [EPK]₀/[initiator]₀, the linear relationship between the feed ratio and M_n of the obtained polymer was observed, while maintaining narrow M_w /M_n. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1073–1082, 2000