Use of Nanomagnetic Sulfated Zirconia (Fe₃O₄@ZrO₂/SO₄²⁻) as Sustainable Heterogeneous Acid Catalyst for Synthesis of Spiroheterocycles under Solvent‐Free Conditions

Abstract

An efficient and environmentally benign domino protocol has been presented for the synthesis of structurally diverse spiroheterocycles spiroannulated with 1,3,4‐thiadiazolo[3, 2‐a]pyrimidine involving three‐ component reaction of 2‐amino‐1,3,4‐thiadiazole, isatin/N‐methyl‐4‐piperidone/1,2‐acenaphthylenedione and carbonyl compounds catalyzed by magnetically recoverable and reusable nanocrytalline sulfated zirconia (Fe3O4@ZrO2/SO42−) under solvent free conditions with grinding at room temperature. The use of magnetically recyclable and reusable catalyst, mild reaction conditions with operational simplicity (grinding), and excellent product yields are significant features of the present synthetic protocol. Moreover, easy magnetic separation of the catalyst eliminates the requirement of catalyst filtration after completion of the reaction and the catalyst remains highly active even after recycled several times.

Synthesis and characterization of terbium doped TiO2 nanoparticles and their use as recyclable and reusable heterogeneous catalyst for efficient and environmentally sustainable synthesis of spiroannulated indolo[3,2‐c]quinolines‐ mimetic scaffolds of isocryptolepine

“…The present synthetic methodology involves the reaction of phenylhydrazine, with o-aminoacetophenone and cyclic ketones using nanostructured Terbium doped TiO 2 as recyclable and reusable heterogeneous catalyst. In view of medicinal importance of isocryptolepine structural framework and our research interest in the synthesis of drug-like hybrid molecules with privileged heterocyclic structures, [34][35][36][37][38][39][40][41][42][43][44][45] the present synthetic protocol is probably the first report for the synthesis of spiroannulated indolo […”

A Green Catalyst Fe(OTs)3/SiO2 for theSynthesis of 4‐Pyrrolo‐12‐oxoquinazolines

“…[2,3] Although a large variety of iron catalyzed reactions are developing for the increasing demand for green and sustainable chemistry, [4,5] iron based heterogeneous acid catalysts have been riveted in the organic synthesis in view of their excellent catalytic performance including ease of separation, recyclability and reusability. [6] However, a variety of heterogeneous catalysts have been efficiently employed in various multicomponent reactions. [7] In this regard, Fe(OTs) 3 / SiO 2 is considered as one of the most important acid catalysts and has been utilized as an effective catalyst in organic transformations due to their high strength of acidity, nontoxicity and high activity at low temperature.…”

“…Iron salts have been focused as attractive catalysts in the field of synthetic chemistry because of their low cost and eco‐friendly character [2,3] . Although a large variety of iron catalyzed reactions are developing for the increasing demand for green and sustainable chemistry, [4,5] iron based heterogeneous acid catalysts have been riveted in the organic synthesis in view of their excellent catalytic performance including ease of separation, recyclability and reusability [6] . However, a variety of heterogeneous catalysts have been efficiently employed in various multicomponent reactions [7] .…”

Multicomponent synthesis of dispiroheterocycles using a magnetically separable and reusable heterogeneous catalyst

“…In view of our continuing efforts to develop environmentally sustainable protocol, [49][50][51][52][53][54][55][56] we have presented synthetic protocol to synthesize a library of dispiroheterocycles incorporating unique combination of three or four privileged substructures.…”