3.1.6. Catalyst activity
Optimization conditions for the one-pot synthesis of ethyl 4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3 carboxylate in the presence of [Bsim] Cl under solvent-free conditions.EntryCatalyst (mol%)Temp (°C)Time (min)Yielda (%)1–6090192360497935602684476015895106089261260493710256063810404278910501984101060892101070592aYields refer to the pure isolated products based on the reaction of 4-methoxybenzaldehyde (10 mmol), dimedone (10 mmol), ethyl acetoacetate (10 mmol) and ammonium acetate (15 mmol).Full-size tableTable optionsView in workspaceDownload as CSV
Further investigation shows that NVP-LAQ824 10 mol% of catalyst at 60 °C is an optimum condition and the product yield was excellent. To investigate the generality of the present protocol, various aldehydes were used and converted to hexahydroquinolines under the optimum conditions (Table 2).
Synthesis of ethyl 4-(aryl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate derivatives catalyzed by [Bsim]Cl.EntryAldehydesProductTime(min)Yielda (%)M.P./M.P. [ref] (°C)1691201–203/203–2052590232–234/233–2353590205–207/207–2094493242–244/242–2445591171–173/172–1746892258–259/257–2597694261–263/262–2648793228–229/228–2309690261–263/262–263101089184–186/184–18611n-heptanal–120––12n-octanal–120––aYields refer to the isolated pure products. The desired known pure products were characterized by comparison of their physical data (melting points, IR, 1H NMR) with secondary structure of known compounds.Full-size tableTable optionsView in workspaceDownload as CSV