α‐Halogenoacetanilides as Hydrogen‐Bonding Organocatalysts that Activate Carbonyl Bonds: Fluorine versus Chlorine and Bromine |
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| Authors: | Dr Sylvain Koeller Dr Coralie Thomas Dr Fréderic Peruch Dr Alain Deffieux Dr Stéphane Massip Prof?Dr Jean‐Michel Léger Dr Jean‐Pierre Desvergne Prof?Dr Anne Milet Dr Brigitte Bibal |
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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)?54000‐6158;2. Laboratoire de Chimie des Polymères Organiques, UMR 5629, Université de Bordeaux and CNRS, 16 avenue Pey‐Berland, 33600 Pessac (France);3. FRE CNRS 3396 Pharmacochimie, Université de Bordeaux, 146 rue Léo Saignat, 33076 Bordeaux (France);4. Département de Chimie Moléculaire, UMR 5250, ICMG FR‐2607, Université Joseph Fourier‐Grenoble I, BP 53, 38041 Grenoble (France) |
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| Abstract: | α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CXn (n=1–2, X=Cl, Br) or a H?CAr bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX2 interaction. |
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| Keywords: | hydrogen bonds lactide noncovalent interactions organocatalysis ring‐opening polymerization |
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