Chapter 5 - Sonochemical protocol for solvent-free organic synthesis

Abstract

Ultrasound irradiation (USI), by virtue of cavitational collapse, is able to conduct diverse organic reactions with outstanding outcomes in terms of reaction rates, yields, and selectivities. On another note, solvent-free synthesis has received considerable attention owing to the rising concern for the effect of solvents on the environment. USI combined with no solvent conditions leads to eco-friendly synthetic conditions together with considerable improved selectivity, cleaner reactions, higher yields and purities, and reduction of reaction times. This chapter includes material illustrating up-to-date developments on US-assisted solvent-free synthesis of heterocyclic compounds. To be more precise, the chapter consists of two parts. The first part deals with US-assisted solvent- and catalyst-free one-pot multicomponent synthesis of 1,4-diazabutadienes, pyrrolidines, α-aminophosphonates, formamidines, pyrazolones, 1,4-dihydropyridines, amines, formamides, and silyl ethers. The second part focuses on US-assisted solvent-free one-pot multicomponent synthesis of trans-chalcones, 3,4-dihydro-2(1H)-quinolinones, imidazoles, coumarins, 1H-1,2,3,4-tetrazoles, β-indolylketones, 1,5-benzodiazepines, α-oxycarbanilinophosphonates, dihydropyrimidinones, β-iodo vinylthiocyanates, α-hydroxyphosphonates, α-aminophosphonates, and 2-aminothiophenes.