C18-DABCO-AA: A Novel Brønsted Acidic Gemini Surfactant for the Environmental Benign Synthesis of 2,3‑Dihydroquinazolin‑4(1H)‑ones in Water at Ambient Temperature

Abstract

We have successfully synthesized a new acidic surfactant named C₁₈-DABCO-AA, which contains octadecyl and acetic acid substituent on DABCO (1,4-diazabicyclo [2.2.2] octane) unit, with an excellent yield. The synthesized surfactant was analyzed using FT-IR, ¹H NMR, and ¹³C NMR spectroscopic techniques. Its thermal behavior was analyzed by using the TGA–DTA technique. Our analysis indicates that the synthesized surfactant has excellent surfactant properties. Its critical micelle concentration (CMC) is 0.80 mM as determined by the conductivity method and UV–vis absorption measurement at 298.15 K. Surfactant also showed strong acidic properties with a pK_a of 3.3. It is the best catalyst for the synthesis of 2,3‑dihydroquinazolin‑4(1H)-ones (DHQs) in water at 40 °C. The synthesis is achieved via two-component reactions of various aromatic aldehydes and anthranilamide in water at a CMC concentration of C₁₈-DABCO-AA. The method was also extended for synthesizing DHQs via two-component reactions of different ketones and anthranilamide under similar reaction conditions. The products were achieved in with yields ranging from good to excellent within 60–90 min. Additionally, the aqueous solution with C₁₈-DABCO-AA was reused up to five times with a minor decrease in product yield. The present protocol is fast, energy-efficient, and can be used on a large scale for synthetic purposes. Additionally, it boasts impressive environmentally friendly credentials.