Synthesis of quinolines via 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 Cu(2+) 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.

Catalytic performance of Metal-Organic-Frameworks vs. extra-large pore zeolite UTL in condensation reactions

“…For zeolites, absorption bands around 1546 cm −1 (interaction of pyridine with Brønsted acid sites) and 1453–1455 cm −1 (interaction of pyridine with Lewis acid sites) were chosen as characteristic. To estimate the acidity of the Cu 3 (BTC) 2 band at 1069 cm −1 assigned to C–C out-of-plane vibrations of coordinatively bonded pyridine was chosen (Pérez-Mayoral et al, 2012). Characteristic bands in region 1400–1600 cm −1 were not used for the determination of the amount of acid sites in MOFs because of an overlap with the bands corresponding to MOF's framework.…”

“…The concentration of coordinatively bonded pyridine was determined to be equal to 2.30 mmol g −1 for Cu 3 (BTC) 2 activated at 200°C (Pérez-Mayoral et al, 2012). …”

“…For the quantitative determination of concentration of relevant acid sites the molar adsorption coefficients (Emeis, 1993) for pyridine adsorbed on Brønsted [ν(C = N) − B at 1540 cm −1 , ε(Br) = 1.67 cm/μmol] and Lewis acid sites [ν(C = N) − L at 1470 cm −1 , ε(L) = 2.22 cm/μmol] were used. Determination of Lewis acid sites in CuBTC is discussed in detail elsewhere (Pérez-Mayoral et al, 2012). …”

Accurate Ab Initio Description of Adsorption on Coordinatively Unsaturated Cu2+ and Fe3+ Sites in MOFs

“…[1][2][3][4][5] MOFs containing coordinatively unsaturated sites (CUSs) are of particular interest due to their adsorption selectivity and potential catalytic applications. [1][2][3][4][5] MOFs containing coordinatively unsaturated sites (CUSs) are of particular interest due to their adsorption selectivity and potential catalytic applications.…”

Oxidative cross-dehydrogenative coupling of amines and α-carbonyl aldehydes over heterogeneous Cu-MOF-74 catalyst: A ligand- and base-free approach

“…During the last few years, many MOFs have been explored as heterogeneous catalysts or catalyst supports in organic synthesis [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. One of the challenges in MOFs catalysis is to make crystals whose pore apertures are of a size suitable for the inclusion of large organic molecules.…”