One pot four component sequential synthesis of hexahydroquinoline derivatives in aqueous media via enaminone intermediates: A green protocol

In situ synthesis of SO3H supported Fe3O4@resorcinol–formaldehyde resin core/shell and its catalytic evaluation towards the synthesis of hexahydroquinoline derivatives in green conditions

“…(i) The addition of ammonium acetate to the dimedone and the formation of enaminone (enaminone possesses the nucleophilic characters of enamine and enone). 57 At this stage, ammonium acetate serves as a source of hydrogen and activates the carbonyl group from dimedone and malononitrile to form enaminone. 57 (ii) A Knoevenagel reaction between the benzaldehyde and the malononitrile gives rise to the formation of arylidenemalononitrile (the ammonium acetate also acts as a base source and converts malononitrile into a nucleophile by removing hydrogen from the malononitrile).…”

“…57 At this stage, ammonium acetate serves as a source of hydrogen and activates the carbonyl group from dimedone and malononitrile to form enaminone. 57 (ii) A Knoevenagel reaction between the benzaldehyde and the malononitrile gives rise to the formation of arylidenemalononitrile (the ammonium acetate also acts as a base source and converts malononitrile into a nucleophile by removing hydrogen from the malononitrile). 58 (iii) A Michael addition reaction involving the intramolecular cyclization between the enaminone and arylidenemalononitrile; water elimination under this condition results in the formation of the nal product (Scheme 1).…”

Tandem Protocol of Hexahydroquinoline Synthesis Using [H2-DABCO][HSO4]2 Ionic Liquid as a Green Catalyst at Room Temperature

“…This cagelike structure increases the energy barrier of nitrogen inversion so the lone pair is localized and makes DABCO more susceptible toward quaternization and ionic liquid preparation and further applied in organic reactions. − Regarding the abovementioned notable properties of 1,4-DHP derivatives, their synthetic methods have been investigated in various environmental conditions. − However, most of the research studies have been done on the synthesis of 3-carboxylate derivatives of 1,4,5,6,7,8-hexahydroquinoline compared to 3-carbonitrile derivatives. 1,4,5,6,7,8-Hexahydroquinoline-3-carbonitrile was previously synthesized using NH 4 OAc, sulfonated rice husk, nanosized MgO, nano-Fe 3 O 4 @TDI@TiO 2 , citric acid/MCM-48, and K 2 CO 3 catalyst. − Despite the undeniable advantages of these processes, some disadvantages are also present, like the involvement of metal catalysts, nonrecyclable catalysts, high catalyst loading, long reaction time, high temperature, and small substrate scope. Therefore, further efforts are needed to present more proficient and eco-benign methods for the synthesis of hexahydroquinoline-3-carbonitriles.…”

Preparation of DABCO‐Based Acidic‐Ionic‐Liquid‐Supported ZnO Nanoparticles and Their Application for Ecofriendly Synthesis of N‐Aryl Polyhydroquinoline Derivatives

“…After successful entry of these drugs in clinical field in the treatment of cardiovascular diseases, further researches were carried out to extend versatility of 1, 4 DHP nucleus. Series of these 1, 4 dihydropyridine derivatives showed diversified medicinal application like HIV protease inhibition, antitubercular, antioxidant, antitumor, antimicrobial and analgesic . A large extent of researches have been carried out to improvise the structure of nifedipine, the archetype of DHPs, in order to boost calcium modulating effects .…”