Efficient and environmentally sustainable domino protocol for the synthesis of diversified dispiroheterocycles using 1-Butyl-3-methylimidazolium bromide [bmim]Br

An environmentally benign, simple, and efficient procedure has been developed for the construct of some symmetrical dispiroheterocycles derivatives by the reaction of the variety of 6-amino-2-thiouracil/6-aminouracil /2-amino-1,3,4-thiadiazole, isatins and p-toluidine in the presence of 1-Butyl-3-methylimidazolium bromide ([bmim]Br) as a solvent as well as catalyst at room temperature. In this study, a variety of bis-spiro-indoline-chromenes, pyranopyranes, imidazo-pyridines, pyrido-pyrimidines and pyridines were obtained with excellent yields within short reaction time and without chromatographic separation. Furthermore, the green catalytic system can be recycled specific times with no decreases in yields and reaction rates.