Facile synthesis of thiochromanyl-spirooxindoles via K 2 CO 3 catalyzed tandem sulfa-Michael/Aldol reaction

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.

Synthesis of 2-substituted 3-chlorobenzofurans via TMSCl-mediated nucleophilic annulation of isatin-derived propargylic alcohols

A TMSCl-mediated cascade annulation of isatin-derived propargylic alcohols for the synthesis of 2-substituted 3-chlorobenzofurans is now reported. Mechanistic investigations showed that this proceeded through a sequential Meyer-Schuster rearrangement/nucleophilic addition/intramolecular annulation. TMSCl not only acts as a promoter, but also acts as a chlorine source in this protocol.

Synthesis of Spiro Thiazolo[3,2-a]Pyrimidine-Tetrahydrothiophenes via Sulfa-Michael/Aldol Cascade Reactions

The sulfa-Michael/aldol cascade reaction of 2-arylmethylidene-6,7-dihydro-2 H-thiazolo[3,2- a]pyrimidin-3(5 H)-ones and 1,4-dithiane-2,5-diol afforded novel 2′-aryl-4′-hydroxy-4′,5′,6,7-tetrahydro-2′ H-spiro[thiazolo[3,2- a]pyrimidine-2,3′-thiophen]-3(5 H)-ones in good yields. The structures of all products were characterised thoroughly by NMR, IR, HRMS, together with X-ray crystallographic analysis.

Synthesis of Spiro Indazole-Tetrahydrothiophenes via Sulfa-Michael/Aldol Cascade Reactions

The sulfa-Michael/aldol cascade reaction of 5-arylmethylidene-1-phenyl-6,7-dihydro-1H-indazol-4(5H)-ones and 1,4-dithiane-2,5-diol yielded novel 2′-(4-aryl)-4′-hydroxy-1-phenyl-4′,5′,6,7-tetrahydro-2′H-spiro[indazole-5,3′-thiophen]-4(1H)-ones in moderate yields. The structures of all the products were characterised thoroughly by NMR, IR and HRMS, together with X-ray crystallographic analysis.