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Hydrogen-Bonding Cyclodiphosphazanes: Superior Effect of 3,5-(CF3)2-Substitution in Anion-Recognition and Counter-Ion Catalysis

Abstract

New HB-cyclodiphosph(V)azanes with a variety of structural modifications, e.g. unsymmetrical substitution of the phosphorus atoms with sulfur and oxygen atoms as well as either phenyl- (O(=P)/S(=P)-13) or 3,5-(CF3)2-C6H3-substitution (O(=P)/S(=P)-14) and 3,5-F2C6H3-substituted cyclodiphosph(V)azanes with either oxygen (O(=P)-15) or sulfur (S(=P)-16) substitution at the phosphorus atoms, are synthesized. These new systems are employed together with sulfur substituted cyclodiphosph(V)azanes with phenyl- (11) and 3,5-(CF3)2-C6H3-substitution (12) in recognitions of chloride and acetate anions. These HB-systems are compared to previously established reference systems, i.e. cyclodiphosph(V)azanes (4, 5), thiourea (20) and squaramides (21, 22). Modifications of the chalcogen atom in the cyclodiphosph(V)azane moieties from oxygen (O(=P)-5) to sulfur (O(=P)/S(=P)-14, S(=P)-12) reveals a decrease in anion binding capabilities. The 3,5-(CF3)2-C6H3 substituted O(=P)-cyclodiphosph(V)azane 5 exhibits the strongest anion binding effect (chloride: 5.91, acetate: 6.06) in acetonitrile, surpassing even the established thiourea 20 (chloride: 4.30, acetate: 5.47) as well as squaramides 21 (chloride: 4.92, acetate: 4.24) and 22 (chloride: 5.13, acetate: 5.37). Computational studies confirm 3,5-(CF3)2-C6H3 substituted 5 to be the strongest here studied anion-binding cyclodiphosph(V)azane with computed binding energies ΔGin-out•Cl of -21.1 kcal/mol and ΔGin-out•OAc of -14.3 kcal/mol, surpassing thiourea 20 (ΔGin-out•Cl = -19.10 kcal/mol, ΔGin-out•OAc = -13.81 kcal/mol). The catalytic efficiency of the 3,5-(CF3)2-C6H3 substituted cyclodiphosph(V)azane 5 is examined in a N-acyl-Mannich reaction, showing a significantly higher reactivity (up to 45 % yield) compared to the alternative hydrogen-bonding catalyst di(1-naphthyl)silanediol 28. In all these applications, the superiority of the 3,5-(CF3)2-C6H3 substitution pattern in combination with O(=P)-groups in the cyclodiphosph(V)azane scaffold is apparent.

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Publication details

The article was received on 29 Nov 2017, accepted on 07 Feb 2018 and first published on 07 Feb 2018


Article type: Paper
DOI: 10.1039/C7NJ04660J
Citation: New J. Chem., 2018, Accepted Manuscript
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    Hydrogen-Bonding Cyclodiphosphazanes: Superior Effect of 3,5-(CF3)2-Substitution in Anion-Recognition and Counter-Ion Catalysis

    B. Goldfuss, F. F. Wolf and J. Neudoerfl, New J. Chem., 2018, Accepted Manuscript , DOI: 10.1039/C7NJ04660J

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