Microwave-mediated three-component condensation of 4-aryl-4-oxobutanoates with ammonium formate furnishes 3-methylidene-5-phenyl-2,3-dihydropyrrolidones in good yield within 2 min. The pyrrolidone products were characterized on the basis of spectral data and X-ray crystal structure analysis. The reaction is found to be general and a variation in the ester and aryl moieties is possible. However, when alkylammonium formate is used only amide products are formed

Studies on the reaction of some 1,5-ketodiesters/1,5-diketones with NaX (X = Cl/Br/I)/DMSO have shown that under microwave/thermal conditions, facileretro-Michael addition (RMA) reaction takes place instead of formation of the expected Krapcho products. Mechanistic studies have shown that the NaI/DMSO system is a better system than NaCl/DMSO or NaBr/DMSO to promote the RMA pathway and DMSO is an essential requirement. The electrophilic halide ion could be involved in this fragmentation reaction.

Facile Michael addition of active methylene compounds to α,Β-unsaturated carbonyl compounds takes place on the surface of potassium carbonate under microwave irradiation. Further studies on microwave-mediated Robinson annulations reveal a convenient and facile method for condensation of chalcone with methylene compounds to furnish cyclohexenones.

Alkylation of dipotassium 2-nitro-1,1-ethylenedithiolate 1 with ethyl 4-chloroacetoacetate 6 in a mixture of MeOH-H₂O (2:1) furnished highly functionalized 3-nitrothiophene 5. Pechmann condensation of 5 with 2-hydroxybenzaldehydes 8a-i, 10 furnished coumarin-3-nitrothiophene conjugates 9a-i, 11.

The reaction of 𝑁-methyl-4-(methylthio)-3-nitro-4𝐻-chromen-2-amine and its derivatives with 4-hydroxy-6-methyl-2𝐻-pyran-2-one in EtOH reflux for 5 min furnish 4-hydroxy-6-methyl-3-(2-(methylamino)-3-nitro-4𝐻-chromen-4-yl)-2𝐻-pyran-2-ones in quantitative yield. By extending EtOH reflux for 2 h, the 4𝐻-chromene 4-hydroxy-2-pyranone conjugates get converted into acetoacetyl coumarins. Similar reaction of 𝑁-methyl-4-(methylthio)-3-nitro-4𝐻-chromen-2-amine and its derivatives with 4-hydroxycoumarin in EtOH reflux furnish 4-hydroxy-2'-(methylamino)-3'-nitro-2𝐻,4'𝐻-3,4'-bichromen-2-ones. In contrast to earlier system, prolonging reflux in EtOH or in 𝑛-PrOH reflux the product gets transformed into trans-ethyl 3-(2-hydroxyaryl)-4-oxo-3,4-dihydro-2𝐻-furo[3,2-c]chromene-2-carboxylates. Thus, facile synthesis and characterization of 4𝐻-chromene 4-hydroxy-2-pyrone, 4𝐻-chromene 4-hydroxycoumarin conjugates, acetoacetyl coumarins and trans2,3-disubstituted dihydrofuro[3,2-c]coumarins is described.