Synthesis of 4‐Hydroxy‐3‐(2‐arylimidazo[1,2‐ a ]pyridin‐3‐yl)quinolin‐2(1 H )‐ones in the Presence of DABCO as an Efficient Organocatalyst

Enzymatic Synthesis of Indole-Based Imidazopyridine using α-Amylase

The imidazo[1,2-a]pyridine scaffold has gained significant attention due to its presence as a lead structure in several commercially available pharmaceuticals like zolimidine, zolpidem, olprinone, soraprazan, etc. Further, indole-based imidazo[1,2-a]pyridine derivatives have been found interesting due to their anticancer and antibacterial activities. However, limited methods have been reported for the synthesis of indole-based imidazo[1,2-a]pyridines. In this study, we have successfully developed a biocatalytic process for synthesizing indole-based imidazo[1,2-a]pyridine derivatives using the α-amylase enzyme catalyzed Groebke-Blackburn-Bienayme (GBB) multicomponent reaction of 2-aminopyridine, indole-3-carboxaldehyde, and isocyanide. The generality and robustness of this protocol were shown by synthesizing differently substituted indole-based imidazo[1,2-a]pyridines in good isolated yields. Furthermore, to make α-amylase a reusable catalyst for GBB multicomponent reaction, it was immobilized onto magnetic metal-organic framework (MOF) materials [Fe3 O4 @MIL-100(Fe)] and found reusable up to four consecutive catalytic cycles without the significant loss in catalytic activity.

Development of CuMnxOy (x = 2, and y = 4)-GO heterostructure for the synthesis of pyranoquinoline derivatives

The pyranoquinoline derivatives are synthetically important due to their biological properties. In this research, these derivatives were produced through an environmentally friendly method. This method includes the use of CuMn_xO_y (x = 2, and y = 4)-GO as a nanocatalyst, which is easy to produce, has excellent performance, cost-effectiveness, and recyclability among its features, and also the use of water as a green solvent. Pyranoquinolines through the one-pot, the multi-component reaction between different derivatives of aryl glyoxal, ethyl cyanoacetate, and 4-hydroxyquinoline-2(1H)-one were synthesized using nanocatalyst, K₂CO_3, and H₂O. Also, the structure of the CuMn_xO_y-GO nanocatalyst was evaluated and confirmed via different analyses. The distinguishing features of this work compared to previous works are easy workup, recyclability of nanocatalyst, facile synthesis process, and provide high yields of products.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.