(Thio)Amidoindoles and (Thio)Amidobenzimidazoles: An Investigation of Their Hydrogen‐Bonding and Organocatalytic Properties in the Ring‐Opening Polymerization of Lactide |
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Authors: | Sylvain Koeller Dr Joji Kadota Dr Frédéric Peruch Dr Alain Deffieux Dr Noël Pinaud Isabelle Pianet Dr Stéphane Massip Dr Jean‐Michel Léger Dr Jean‐Pierre Desvergne Dr Brigitte Bibal Dr |
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Institution: | 1. Institut des Sciences Moléculaires UMR CNRS 5255, Université de Bordeaux, 351 cours de la Libération, 33405 Talence (France), Fax: (+33)?5‐4000‐6158;2. Laboratoire de Chimie des Polymères Organiques, Ecole Nationale Supérieure de Chimie et Physique de Bordeaux, 16 avenue Pey‐Berland, 33607 Pessac (France);3. Université de Bordeaux, EA 4138 Pharmacochimie, 146 rue Léo Saignat, 33076 Bordeaux (France) |
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Abstract: | The mechanism of the ring‐opening polymerization (ROP) of lactide catalyzed by two partner hydrogen‐bonding organocatalysts was explored. New amidoindoles 4 a , c , thioamidoindoles 4 b , d , amidobenzimidazoles 5 a , c , and thioamidobenzimidazoles 5 b , c were synthesized and used as activators of the monomer. In the solid state and in solution, compounds 4 and 5 showed a propensity for self‐association, which was evaluated. (Thio)Amides 4 and 5 do catalyze the ROP of lactide in the presence of a cocatalyst, tertiary amine 3 a or 3 b , which activates the growing polymer chain through hydrogen‐bonding. Reactions were conducted in 2–24 h at 20 °C; conversion yields ranged between 22 and 100 %. A detailed study of the intermolecular interactions undertaken between the participating species showed that, as expected, simultaneous weak hydrogen bonds do exist to activate the reagents. Moreover, interactions have been revealed between the partner catalysts 4 / 5 + 3 . ROP catalyzed by these partner activators is thus governed by multiple dynamic equilibria. The latter should be judiciously adjusted to fine‐tune the catalytic properties of (thio)amides and organocatalysts, more generally. |
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Keywords: | hydrogen bonds lactides organocatalysis partner catalysts ring‐opening polymerization |
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