Synthesis and photopolymerizations of new phosphonated monomers for dental applications

Three novel phosphonated methacrylate monomers have been synthesized and studied for use in dental applications. Two of the monomers were synthesized from the reactions of glycidyl methacrylate (GMA) with (diethoxy-phosphoryl)-acetic acid (monomer 1) and (2-hydroxy-ethyl)-phosphonic acid dimethyl ester (monomer 2). These monomers showed high crosslinking tendencies during thermal bulk and solution polymerizations. The third monomer (monomer 3) was prepared by the reaction of bisphenol A diglycidylether (DER) with (diethoxy-phosphoryl)-acetic acid and subsequent conversion of the resulting diol to the methacrylate with methacryloyl chloride. The homopolymerization and copolymerization behaviors of the synthesized monomers were also investigated with glycerol dimethacrylate (GDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2-bis[4-(2-hydroxy-3-methacr loyloxy propyloxy) phenyl] propane (bis-GMA) using photodifferential scanning calorimetry at 40 degrees C using 2,2-dimethoxy-2-phenyl acetophenone (DMPA) as photoinitiator. Monomer 1 showed polymerization rate similar or greater than dimethacrylates studied here but with higher conversion. The maximum rate of polymerizations decreased in the following order: 1 similar to TEGDMA > GDMA-bis-GMA similar to 3 > 2. A synergistic effect in the rate of polymerization was observed during copolymerizations. (c) 2008 Wiley Periodicals, Inc

Mechanism switch in Mannich-type reactions. ELF and NCI topological analyses of the reaction between nitrones and lithium enolates

The mechanism of the addition of lithium enolates derived from esters, ketones and aldehydes to nitrones (Mannich-type reaction) has been studied using DFT methods. While the reactions with α-methoxy and α-methyl enolates takes place through a stepwise mechanism, consisting of an initial nucleophilic attack of the enolate to the nitrone carbon followed by a second nucleophilic attack of the nitrone oxygen to the formed carbonyl group, the reaction with α-unsusbtituted enolates takes place through a one-step mechanism. The IRC analysis shows the presence of a hidden intermediate in agreement with one kinetic step two stages process. The topological analysis of the electronic localization function (ELF) confirms that only when the first C-C bond is formed, does the C-O bond formation begin. The NCI analyses, are also in agreement with the formation of intermediates for α-methoxy and α-methyl enolates and a highly asynchronous one-step process in the case of α-unsusbtituted enolates.This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) (project number CTQ2013-44367-C2-1-P), by the Fondos Europeos para el Desarrollo Regional (FEDER) and the Gobierno de Aragón (Zaragoza, Spain, Bioorganic Chemistry Group, E-10). D. R.-L. thanks the Spanish Ministry of Education (MEC) for a pre-doctoral grant (FPU program).Peer reviewe