Dehydration in Water: A Reagentless and Straightforward Synthesis of Tetrahydroquinazolines under Microwave Irradiation or by Stirring at Room Temperature, and Their Subsequent Conversion into Quinazolines in a Micellar Medium

Abstract

In a reagent-free, catalyst-free approach, a series of 2-substituted-1,2,3,4-tetrahydroquinazolines were synthesized by cyclo-condensation between various aldehydes and 2-aminobenzylamines via dehydration reaction in water. The reactions took just 2 min under microwave irradiation and proceeded well under stirring at room temperature affording tetrahydroquinazolines in high to excellent yields. The products were water-insoluble and isolated by simple filtration avoiding a conventional work-up step and offering an organic solvent-free process. Furthermore, terahydroquinazolines were efficiently oxidized to quinazolines in cetyltrimethylammonium bromide (CTAB) derived micellar media with cheap commercial bleaching solution (4% NaOCl in water) in high yields. This sustainable protocol has near zero E-factor.