Fe(OTs)₃/SiO₂: a novel catalyst for the multicomponent synthesis of dibenzodiazepines under solvent-free conditions

Abstract

A novel heterogeneous catalyst Fe(OTs) 3 /SiO 2 was synthesized and identified using FT-IR, XRD, SEM, EDX, XRF and TG analyses. The catalyst was successfully applied as a highly effective catalyst for the synthesis of a series of dibenzodiazepines under solvent-free condition. This protocol has the advantages of convenient one-pot operation, atom-economy, excellent yields in short reaction time, reusability of catalyst and environmental friendliness. 4 oxalic acid/water, acetic acid/i-propanol and sulphuric acid/ethanol which have drawbacks like use of non-recyclable catalyst, long reaction time and environmental hazards. [14][15][16][17] However, some improved methods are also reported which includes use of ZnS NPs and chitosan-Fe 3 O 4 , etc. 18,19 In this regard, exploring alternative catalysts for synthetic improvement of this reaction, we have synthesized a novel catalyst Fe(OTs) 3 /SiO 2 and analysed its catalytic potential for the synthesis of dibenzodiazepines via three-component reaction of dimedone, o-phenylenediamine and aldehydes/hetero aldehydes. The newly synthesized catalyst has been characterized with the help of FT-IR spectra, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray fluorescence (XRF) techniques. Thermal stability of the catalyst is examined by TG analysis. Results and Discussion Characterization of catalyst Fe(OTs) 3 /SiO 2 FT-IR spectrum of Fe(OTs) 3 /SiO 2The FT-IR spectrum of SiO 2 (Fig. 1a) showed a broad OH stretching absorption band in the region of 3422 cm -1 . The bands at 1110 cm -1 and 808 cm -1 were attributed to anti-symmetric and symmetric Si-O-Si stretching vibrations. Si-O-Si bending mode appeared near 473 cm -1 . For comparative analysis, the FT-IR spectrum of Fe(OTs) 3 is also included (Fig. 1b).The spectrum exhibited characteristic peaks at 3071 cm -1 and 1037 cm -1 for C-H stretching and bending vibrations. The peaks at 1262 and 1158 cm -1 were indicative of the O=S=O asymmetric and symmetric stretching vibrations, respectively. C-S stretching mode was observed at 567 cm -1 . 20

Metal‐Catalyzed Routes to Dibenzodiazepines (DBDAs) and Structural Analogues: Recent Advances

“…[46][47][48][49] Recently, Tarannum and Siddiqui [50] reported a novel catalytic system, that consisted of Fe(OTs) 3 / SiO 2 , which was used for the multicomponent synthesis of the dibenzodiazepine analogues 29 (which contained only one benzene unit) under solvent-free conditions (Scheme 16). Its lack of sensitivity to moisture, ease in handling and low toxicity makes it an attractive catalyst for organic synthesis.…”

“…Its lack of sensitivity to moisture, ease in handling and low toxicity makes it an attractive catalyst for organic synthesis. [46][47][48][49] Recently, Tarannum and Siddiqui [50] reported a novel catalytic system, that consisted of Fe(OTs) 3 / SiO 2 , which was used for the multicomponent synthesis of the dibenzodiazepine analogues 29 (which contained only one benzene unit) under solvent-free conditions (Scheme 16). The Fe(OTs) 3 /SiO 2 catalyst was easily prepared by adding Fe(OTs) 3 to a suspension of silica gel in ethanol.…”

Graphene‐mesoporous anatase TiO2 nanocomposite: A highly efficient and recyclable heterogeneous catalyst for one‐pot multicomponent synthesis of benzodiazepine derivatives

“…Thus, the incorporation of graphene in the Gr@TiO 2 NCs not only increased the specific area, but also made the active center Ti well dispersed among the catalyst, which made the catalyst structure rather more stable and dramatically improved the catalytic activity compared with pure TiO 2. Functionalized TiO 2 NPs is extensively utilized in catalytic activity, few of them such as ZnO NPs, ZnS NPs, chitosan‐Fe 3 O 4, Fe(OTs) 3 /SiO 2 , Fe 3 O 4 @TiO 2 @O 2 PO 2 (CH 2 )NHSO 3 H, cellulose‐based magnetic NCs, silica‐based magnetic NCs, Fe 3 O 4 /SBA‐15, Fe 3 O 4 @cellulose, chitosan/graphene oxide, cellulose/Ag, CoFe 2 O 4 @B 2 O 3 ‐SiO 2 , SO 3 H‐functionalized magnetic core/shell, cellulose/γ‐Fe 2 O 3 /Ag NCs, graphene oxide‐chitosan and Fe 3 O 4 /SiO 2 are a few magnitude higher than TiO 2 NPs with limited surface area . Hybrid material graphene‐TiO 2 , π‐π noncovalent bonded with graphene, will be able to retain their stability and catalytic activity in the challenging organic reactions like the synthesis of benzodiazepine.…”

“…Both the catalyst were synthesized through wet chemical route. To choose the synthesis of benzodiazepines owing its biological importance such as analgesic, anti‐inflammatory, antipyretic, anti‐cancer, anticonvulsant, antimicrobial, anthelmintic, antianxiety and anti‐depressive activities . Herein, we explore the potential catalytic activity of TiO 2 NPs and its comparable Gr@TiO 2 NCs in the synthesis of benzodiazepines through the reaction of dimedone, o ‐phenylenediamine and aromatic aldehydes.…”

SnO2 nanoparticles as an efficient heterogeneous catalyst for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones

“…MCRs with heterogeneous catalyst and solvent-free process are more attractive to the researchers, because they will minimize the waste and usage of hazardous chemicals [31,32]. Moreover, the heterogeneous catalysts have more enrapture to the researchers because of their selectivity and reactivity in organic transformations [33][34][35] and they provide more advantages over homogeneous catalysts due to the more active sites. In addition, they are environmental friendly, cost effective, insoluble in solvents and reusable leading to easy work-up procedures.…”