Enhanced Catalytic Properties of Carbon supported Zirconia and Sulfated Zirconia for the Green Synthesis of Benzodiazepines

Abstract

This work reports for the first time a new series of promising porous catalytic carbon materials, functionalized with Lewis and Brønsted acid sites useful in the green synthesis of 2,3‐dihydro‐1H‐1,5‐benzodiazepine – nitrogen heterocyclic compounds. Benzodiazepines and derivatives are fine chemicals exhibiting interesting therapeutic properties. Carbon materials have been barely investigated in the synthesis of this type of compounds. Two commercial carbon materials were selected exhibiting different textural properties: i) Norit RX3 (N) as microporous sample and ii) mesoporous xerogel (X), both used as supports of ZrO2 (Zr) and ZrO2/SO42− (SZr). The supported SZr led to higher conversion values and selectivities to the target benzodiazepine. Both chemical and textural properties influenced significantly the catalytic performance. Particularly relevant are the results concerning the non‐sulfated samples, NZr and XZr, that were able to catalyze the reaction leading to the target benzodiazepine with high selectivity (up to 80 %; 2 h). These results indicated an important role of the carbon own surface functional groups, avoiding the use of H2SO4. Even very low amounts of SZr supported on carbon reveal high activity and selectivity. Therefore, the carbon materials herein reported can be considered an efficient and sustainable alternative bifunctional catalysts for the benzodiazepine synthesis.

Eco‐sustainable Synthesis of N‐containing Heterocyclic Systems Using Porous Carbon Catalysts

“…These authors also prepared a series of carbon supported zirconia or sulfated zirconia involved on the selective green synthesis benzodiazepine, confirming that the presence of À SO 3 H functions on either zirconia or anchored onto the carbon surface, considerably improved the selectivity. [83] In addition, stronger acid sites anchored to the carbon surface and the high microporosity of ACs modified with different acids are responsible by the selectivity enhancement. [84] Much more recently, highly macroporous carbons from pyrolysis of spent tires to avoid diffusional restrictions, under mild reaction conditions, were also reported for benzodiazepine synthesis.…”

“…Benzodiazepines are among the most prescribed drugs worldwide mainly by their psychotropic activity. Assuming that sulfated zirconia (SZr) is a widely used catalyst in industrial transformations, Godino-Ojer et al [83] recently, published a new family of zirconia (Zr) and SZr/carbon composites active for the green synthesis of 2,3-dihydro-1H-1,5-benzodiazepines (Scheme 31). In this study, it was demonstrated that the Zr sample promotes the first reaction step to give the 2,3-dihydrobenzimidazole, while the Brönsted acid centers in SZr are involved in the final electrocyclization reaction affording the corresponding benzodiazepine.…”

Making more with less: confinement effects for more sustainable chemical transformations

“…Godino-Ojer et al studied the synthesis of benzodiazepines, which are nitrogen-containing heterocyclic compounds of great importance as pharmaceuticals. 79 Specifically, the authors looked at the reaction of o -phenyldiamine with different ketones catalyzed by sulfated zirconia (Scheme 8). Carbon xerogels (mesoporous) and microporous carbon were tested as supports, and the supported catalysts gave improved selectivity to the desired benzodiazepines.…”

Enhanced catalytic performance of ZnO/carbon materials in the green synthesis of poly-substituted quinolines

“…The selection of the carbon supports from commercial AC, pure carbon gel [19] to functionalized CNTs, providing a wide variety of both textural, morphological, and chemical properties is motivated by our own experience and other authors actively investigating with this type of carbon materials for the Friedländer reaction, as above mentioned, and other fine chemicals synthesis [26,27]. Nevertheless, other inorganic solids such as a commercial Znbased MOF (Basolite® Z1200) and Zn-catalyst supported on mesoporous silica (SBA-15) have been also investigated for further comparisons.…”