A green method for solvent-free conversion of epoxides to thiiranes using NH4SCN in the presence of NiFe2O4 and MgFe2O4 magnetic nanocatalysts

NiFe2O4@SiO2-Cu as a novel and efficient magnetically recoverable nanocatalyst for regioselective synthesis of β-thiol-1,2,3-triazoles under benign conditions

A green, mild and eco-friendly approach for the three component one-pot regioselective synthesis of 1,2,3-triazoles from thiiranes has been introduced in the presence of NiFe2O4@SiO2-Cu as a new and recoverable nanocatalyst. First, the NiFe2O4 nanoparticles have been produced through a solid-state reaction of hydrated nickel sulfate, hydrated iron(iii) nitrate, NaOH and NaCl salts, and then calcined at 700 °C. Next, in order to protect the ferrite particles from oxidation and aggregation, the NiFe2O4 was core-shelled using tetraethyl orthosilicate (TEOS) and converted to NiFe2O4@SiO2. Finally, the novel NiFe2O4@SiO2-Cu nanocomposite was successfully prepared by adding copper(ii) chloride solution and solid potassium borohydride. The catalyst has been characterized by FT-IR, SEM, EDX, VSM, ICP-OES, TEM and XRD techniques. The 1,3-dipolar cyclization of 1,2,3-triazoles was performed successfully in water at room temperature in high yields. The recoverability and reusability of the heterogeneous NiFe2O4@SiO2-Cu have also been investigated using VSM, SEM and FT-IR analyses. The catalyst was used four times in consecutive runs without considerable loss of activity. The presented procedure provides significant benefits such as using water as a green solvent, absence of hazardous organic solvents, high yields, benign conditions and recyclability of the magnetic catalyst.

Fe3O4@SiO2-PMA-Cu magnetic nanoparticles as a novel catalyst for green synthesis of β-thiol-1,4-disubstituted-1,2,3-triazoles

The magnetic nanoparticles of Fe₃O₄ were synthesized through a solid-state reaction of hydrated iron (III) chloride, hydrated iron (II) chloride and NaOH, and then purified by calcination at high temperature. In order to protect ferrite nanoparticles from oxidation and agglomeration, and to manufacture a novel catalytic system of anchored copper on the magnetic substrate, the Fe₃O₄ was core-shelled by adding tetraethyl orthosilicate. Next, the prepared Fe₃O₄@SiO₂ was supported by phosphomolybdic acid (PMA) as the second layer of nanocomposite at 80 °C in 30 h. Eventually, the new nanocomposite of Fe₃O₄@SiO₂-PMA-Cu was successfully synthesized by adding copper (II) chloride solution and solid potassium borohydride. The structure of magnetic nanocatalyst was acknowledged through different techniques such as EDS, VSM, XRD, TEM, FT-IR, XPS, TGA, BET and FESEM. The synthesis of β-thiolo/benzyl-1,2,3-triazoles from various thiiranes, terminal alkynes and sodium azide was catalyzed by Fe₃O₄@SiO₂-PMA-Cu nanocomposite in aqueous medium. In order to obtain the optimum condition, the effects of reaction time, temperature, catalyst amount and solvent were gauged. The recycled catalyst was used for several consecutive runs without any loss of activity.

Green synthesis of various saturated S-heterocyclic scaffolds: an update

Development of reliable and eco-friendly novel schemes for the synthesis of organic compounds is an important step in the field of organic and medicinal chemistry. Green chemistry-based strategies involving use of catalysts, green solvents, atom economic reactions etc. play a key role because of their exceptional ability to minimize the toxicity or hazards of the side products and processes. With the use of these green techniques, a number of researchers were able to synthesis a wide range of heterocyclic compounds. This chapter highlights the potential and diverse biological activities of saturated sulphur containing heterocyclic compounds including thiirane, thiane, thiolane and many more. The aim of this chapter is to provide fresh perspective on the various techniques employed for the formation of C–S bond by summarizing all green synthesis from 2016 to 2021.

Preparation, characterization and application of MgFe2O4/Cu nanocomposite as a new magnetic catalyst for one-pot regioselective synthesis of β-thiol-1,4-disubstituted-1,2,3-triazoles

Magnesium ferrite magnetic nanoparticles were synthesized by a solid-state reaction of magnesium nitrate, hydrated iron(iii) nitrate, NaOH and NaCl salts and then calcined at high temperatures. In order to prevent oxidation and aggregation of magnesium ferrite particles, and also for preparing a new catalyst of supported copper on the magnetic surface, the MgFe2O4 was covered by copper nanoparticles in alkaline medium. Magnetic nanoparticles of MgFe2O4/Cu were successfully obtained. The structure of the synthesized magnetic nanoparticles was identified using XRD, TEM, EDS, FT-IR, FESEM and VSM techniques. The prepared catalyst was used in the three component one-pot regioselective synthesis of 1,2,3-triazoles in water. The various thiiranes bearing alkyl, allyl and aryl groups with terminal alkynes, and sodium azide in the presence of the MgFe2O4/Cu nanocatalyst were converted to the corresponding β-thiolo/benzyl-1,2,3-triazoles as new triazole derivatives. The effects of different factors such as time, temperature, solvent, and catalyst amount were investigated, and performing the reaction using 0.02 g of catalyst in water at 60 °C was chosen as the optimum conditions. The recovered catalyst was used several times without any significant change in catalytic activity or magnetic property.

CoFe2O4/Cu(OH)2 magnetic nanocomposite: an efficient and reusable heterogeneous catalyst for one-pot synthesis of β-hydroxy-1,4-disubstituted-1,2,3-triazoles from epoxides

A magnetically separable CoFe₂O₄/Cu(OH)₂ nanocomposite was prepared and characterized by various techniques such as FESEM, EDS, TEM, XRD, VSM and FT-IR. This novel composite was used as a heterogeneous catalyst for the regioselective synthesis of β-hydroxy-1,4-disubstituted-1,2,3-triazoles from sodium azide, terminal alkynes and structurally different epoxides in water at 60 °C. The formation of the product proceeds in one pot through a mechanism that involves an in situ generated organic azide intermediate, followed by rapid ring closure with the alkyne component. The simple procedure, short reaction times, perfect regioselectivity, high product yields, and use of a benign solvent and nontoxic catalyst are among the considerable advantages of this protocol. Furthermore, the catalyst was easily separated using an external magnet and reused several times without any significant loss of catalytic activity or magnetic properties.

Magnetically separable CoFe₂O₄/Cu(OH)₂ nanocomposite was prepared and used as a novel heterogeneous catalyst for synthesis of β-hydroxy-1,4-disubstituted-1,2,3-triazoles from epoxides.