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
Dy(III) supported Chitosan nanocatalyst was synthesised by a simple procedure. It was used as catalyst for one pot, three component synthesis of hexahydropyrimidine derivatives. All the reactions were completed in short time period at room temperature and the products were obtained in high to excellent yields. The catalyst was characterized by FT-IR, XRD, SEM-EDX, TEM and ICP-AES analyses. The stability of the catalyst was evaluated by TG analysis. Use of water, ambient conditions, recyclability and high TOF of the catalyst make this protocol a sustainable alternative to existing protocols.
A mild one-pot stereospecific synthetic route to highly
functionalized
imidazolidines and oxazolidines via SN2-type ring-opening
of the corresponding activated aziridines and epoxides with amines
followed by p-toluenesulfonic acid (PTSA)-catalyzed
intramolecular cyclization with aldehydes has been developed. The
methodology tolerates a variety of functional groups and furnishes
the desired products in high yields (up to 92%) with excellent stereoselectivities
(de, ee > 99%). Interestingly, imidazolidines were formed as the
cis-isomers,
whereas oxazolidines were produced as trans-isomers exclusively.
Xanthan sulfuric acid (XSA) is found to be an efficient catalyst for the electrophilic substitution reaction of indole with aromatic aldehydes to afford the corresponding bis(indolyl)methanes at room temperature under solvent-free conditions. The catalyst was characterized for the first time with the help of powder XRD, SEM-EDX and DSC-TGA. The attractive features of this green, new methodology are excellent yield of products, clean reaction profile, reusability of the catalyst, energy sustainable protocol, simple experimental and easier work-up procedures.
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