A multicomponent, facile and catalyst-free microwave-assisted protocol for the synthesis of pyrazolo-[3,4-b]-quinolines under green conditions

Abstract

A facile, swift and ecofriendly microwave-assisted multi-component/one-pot protocol is designed for the synthesis of novel pyrazolo-[3,4-b]-quinolines at ambient temperature in aqueous ethanol as a reaction medium.

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

“…The stated protocol reveals an efficient strategy to produce fused pyrazoloquinolines in good to excellent yields with good functional group tolerance. In 2019, a very similar approach was demonstrated by Jonnalagadda and co-workers [134] with 5-amino-3-methyl-1-phenylpyrazole (150), aldehyde 5, cyclic 1,3-diketone like dimedone (6a) under microwave irradiation in a solvent mixture of water and ethanol at 50 °C. The constructed pyrazolo [3,4-b]…”

“…They are also promising antiviral, antiulcer, anxiolytic, antiherpes agents [115][116][117][118][119]. Similarly, pyrazolo-pyridines are found to be potent antibacterial (131), cytotoxic (132), antiproliferative (133) and antimalarial (134) agents (Figure 10) [120,121].…”

Electrocatalytic Multicomponent Transformation of Aldehyde, 5‐Amino‐3‐methyl‐1‐phenylpyrazole and Dimedone: An Efficient Protocol for Substituted Pyrazolo[3,4‐b]quinolines

“…In addition, Jonnalagadda S. B. et al. reported that microwave irradiation could also facilitate the preparation of pyrazolo[3,4‐ b ]quinoline derivatives in high yield without catalysts [18] . However, the above protocols, although successful, have some inherent limitations, such as high reaction temperatures, toxic noble metal catalysts, longer reaction times, harsh conditions, etc.…”

A Facile and Catalyst-Free Microwave-Promoted Multicomponent Reaction for the Synthesis of Functionalised 1,4-Dihydropyridines With Superb Selectivity and Yields

“…MW induces the growth of oscillation excitation and mass transference in a microwave environment, which produces vigorous heating in reaction vessels, an alternative energy source of chemical reaction for enhanced reaction rate (Polshettiwar and Varma, 2008). Furthermore, the MW technique has attracted considerable interest in organic synthesis due to the higher selectivity, improved product yield, and atom economy, which reduce the by-product generation compared to conventional thermal heating techniques (Khumalo et al, 2019). Therefore, MW-mediated organic synthesis is the preferred green method over unconventional to classical thermal processes for the rapid synthesis of a series Graphical Abstract | Synthesis of Fictionalized 1,4-Dihydropyridines Under Microwave Irradiation and Aqueous Conditions.…”