Synthesis of 8-Quinolinol Mannich Reaction Products

Abstract

Objective: To synthesize biologically significant molecules applying Mannich reaction conditions.
Method:  Equimolar quantities of corresponding aldehydes and amines were mixed with 8-quinolinol (8-HQ) in absolute ethanol at room temperature and pressure without using any catalyst. The reaction progress was monitored through TLC.
Results: The condensation of privileged 8-quinolinol (8-HQ, 1) with various substituted aldehydes and amines has resulted in the synthesis of ten products (2-11) under Mannich reaction conditions. These include four Mannich bases (2-5), three bis-products (6-8) and three imines (9-11). Nine of these derivatives are new and only one of them is known (11). The chemical characterizations of these molecules have been made through extensive study of ¹H, ¹³C NMR and 2D NMR techniques. The long range interaction of H-4 and H-5 with C-10 in HMBC plot, revised the assignment of C-9 and C-10 in 8-quinolinol moiety of newly synthesized derivatives.
Conclusion: Several new derivatives of 8-quinolinol have been prepared under Mannich reaction condition without any catalyst. Exact characterization of these new molecules will serve as a reference spectral data for future study. As Mannich products generally possess significant biological properties, future pharmacological study may turn them as an important target for drug synthesis.