A solvent-free synthesis of polyhydroquinolines via Hantzsch multicomponent condensation catalyzed by nanomagnetic-supported sulfonic acid

Abstract

A simple and efficient procedure for the synthesis of polyhydroquinolines was developed, involving a one-pot four-component Hantzsch condensation of aromatic aldehydes, 1,3-cyclohexanediones, alkyl acetoacetate and ammonium acetate in the presence of a catalytic amount of nanomagnetic-supported sulfonic acid under solvent-free conditions. The method offers several advantages including high yields, short reaction times, a simple work-up procedure and catalyst reusability for several runs. Furthermore, easy isolation of the catalyst from the reaction mixture was enabled by use of an external magnet.

Autocombustion‐Promoted Synthesis of Lanthanum Iron Oxide: Application as Heterogeneous Catalyst for Synthesis of Piperidines, Substituted Amines and Light‐Assisted Degradations

“…Higher temperatures resulted into the decrease in the yield of the desired product because of the formation of byproducts as observed by TLC. [88] Further, in order to investigate the effect of the solvents on the reaction, screening of the different solvents varying from polar to non-polar was done. For this, the reaction was performed at room temperature using 10 mg of catalyst in the presence of 4 ml of different solvents such as EtOH, MeOH, H 2 O, EtOH:H 2 O (1 : 1), MeOH:H 2 O (1 : 1), acetonitrile, DCM, THF and toluene.…”

Quaternary Vanado‐Molybdotungstophosphoric Acid [H5PW6Mo4V2O40] Over Natural Montmorillonite as a Heterogeneous Catalyst for the Synthesis 4H‐Pyran and Polyhydroquinoline Derivatives

“…[62][63][64] Synthesis of polyhydroquinoline derivatives is an interesting research challenge to synthetic chemists. Several improved methods for the synthesis of polyhydroquinoline derivatives such as CoFe 2 O 4 @Pr, [65] molecular iodine, [66] Fe 3 O 4 @chitosan, [67] Thiamine hydrochloride (Vitamin-B 1 ), [68] Amberlite IRA 900, [69] Nano-g-Fe 2 O 3 -SO 3 H, [70] p-toluenesulfonic acids, [71] Sulfamic acids (NH 2 SO 3 H), [72] SiO 2 @Fe 3 O 4 , [73] Gd(OTf) 3 , [74] and Fe 3 O 4 -SA-PPCA [75] have been reported. However, these procedures suffer some drawbacks still exist, such as volatile organic solvents, long reaction time, low yields, expensive catalysts, critical product isolation, and catalyst recycling.…”

Our Contributions in Synthesis of Diverse Heterocyclic Scaffolds by Using Mixed Oxides as Heterogeneous Catalysts

“…Michael addition occurs between the imine intermediate and 5,5‐dimethyl‐1,3‐cyclohexanedione and then further cyclisation yields the required 1,4‐dihydropyridine in a short span (>20 min) (Scheme ). Nano‐γ‐Fe 2 O 3 ‐SO 3 H was employed by Otokeshn et al., under solvent free condition at a 60 °C for 65 min, the activity of catalyst is up to 5 cycles and the product yield is 89–98 %.Thus V 2 O 5 /ZrO 2 serves as an sustainable catalyst in the synthesis of substituted 1,4‐dihydropyridine derivatives, which are widely used as a calcium channel blockers, under room temperature conditions.…”