Synthesis of quinolinesvia Friedländer reaction catalyzed by CuBTC metal–organic-framework

Abstract

Friedländer condensation between 2-aminoaryl ketones and different carbonyl compounds, catalyzed by CuBTC was investigated by a combination of various experimental techniques and by density functional theory based modelling. CuBTC exhibiting hard Lewis acid character showed highly improved catalytic activity when compared with other molecular sieves showing high concentraion of Lewis acid sites, e.g. in BEA and (Al)SBA-15. Polysubstituted quinolines were synthesized via a Friedländer reaction catalyzed by CuBTC under the solvent-free conditions. High concentration of active sites in CuBTC together with the concerted effect of a pair of adjacent Cu²⁺ coordinatively unsaturated active sites are behind a very high quinoline yield reached within a short reaction time. Results reported here make CuBTC a promising catalyst for other Lewis acid-promoted condensations, including those leading to biologically active compounds with a particular relevance for the pharmaceutical industry. The mechanism of a catalyzed Friedländer reaction investigated computationally is also reported.