Room-Temperature Ionic Liquid–DMSO Promoted and Improved One-Pot Synthesis of 5,6-Diaryl-1,2,4-triazines

An improved and rapid one-pot synthesis of 5,6-diarylsubstituted-1,2,4-triazines in a mixture of room-temperature ionic liquid 1,3-dibutylimidazolium bromide [Bbim]⁺Br⁻ and dimethylsulfoxide (DMSO) is described without the need for any added catalyst. Different polar aprotic solvents were screened along with ionic liquids and a synergistic effect with DMSO has been found. The predominance of one regioisomer over the other has also been studied with varying reaction temperatures. The one-pot methodology leading to excellent isolated yields in short span of time is achieved by simple workup procedure. The ionic liquid was efficiently recovered and reused three times without the loss of catalysis. All the compounds were characterized by infrared, NMR, mass spectrometry, and elemental analysis.