Aqueous hydrotropic solution: green reaction medium for synthesis of pyridopyrimidine carbonitrile and spiro-oxindole dihydroquinazolinone derivatives

From the green chemistry point of view, water is one of the most sustainable solvents for chemical transformations, but there are some limitations to its use as a reaction medium due to the lack of solubility of organic compounds. To overcome this difficulty, we used aqueous hydrotropic solution, which increases the solubility of organic compounds in water by 200-fold. We report an environmentally efficient method for synthesis of pyridopyrimidine carbonitriles and spiro-oxindole dihydroquinazolinones by using 50 % aqueous sodium p-toluene sulfonate (NaPTS) solution at ambient reaction condition. The merits of the present protocol include short reaction time, excellent product yield with high purity, easy workup procedure and reusability of reaction medium.