ABSTRACT
Herein, we demonstrate a simple, reproducible, and environment-friendly strategy for the synthesis of carbon quantum dots (CQDs) utilizing the mango (Mangifera indica) kernel as a renewable green carbon source. Various analytical tools characterized the as-prepared CQDs. These fluorescent CQDs showed significant water solubility with a uniform size of about 6 nm. The as-synthesized CQDs show significantly enhanced catalytic activity for the production of α,ß-unsaturated compounds from the derivatives of aromatic alkynes and aldehydes under microwave irradiation in aqueous media. A potential mechanistic pathway and role of carboxylic functionalities were also revealed via various control experiments. The protocol shows outstanding selectivity towards the assessment of α,ß-unsaturated compounds over other possible products. A comparative evaluation suggested the as-synthesized CQDs show higher catalytic activity under microwave radiation as compared to the conventional ways. These recyclable CQDs represent a sustainable alternative to metals in synthetic organic chemistry. A cleaner reaction profile, low catalyst loading, economic viability and recyclability of the catalyst, atom economy, and comprehensive substrate applicability are additional benefits of the current protocol according to green chemistry.
ABSTRACT
Functionalized graphitic carbon nitride (Sg-C3N4) has been manufactured and used as a reusable catalyst for the one-pot production of various spiro-pyrano chromenes and spiro indole-3,1'-naphthalene tetracyclic systems in aqueous media. An ultrasound-assisted method has been used for the functionalization of g-C3N4. The catalytic functionalities and the structural integrity of the catalyst were characterized via different analytical tools. The catalytic site-specific role of Sg-C3N4 was confirmed via various control experiments in one-pot reaction sequences. We recognized that Sg-C3N4 acts as a bifunctional acid-base catalyst for the first reaction sequence whereas it is an acidic catalyst for the second reaction sequence during the one-pot production of various spiro-pyrano chromenes. In addition, the bifunctional acid-base catalytic role of Sg-C3N4 has been confirmed for the first reaction sequence whereas it has a basic catalytic role for the second reaction sequence during the one-pot production of spiro indole-3,1'-naphthalene tetracyclic systems. Diverse C-C, C-O, and C-N bonds, six-membered cycles, stereogenic centers, and spiro frameworks were formed in a single reaction, enhancing the biocidal profile and possibly resulting in the discovery of new medicinal properties. The mild reaction environment, simple workup, easy separation, low cost, heterogeneity, and recyclability of Sg-C3N4 are some rewards of this approach.
ABSTRACT
A simple, environmentally benign and highly proficient microwave assisted one-pot approach for the synthesis of antimicrobial spiropyrrolidine/thiapyrrolizidine oxindole derivatives is reported assembling two pharmacophoric moieties (1,3-indanedione and pyrrolidine/thiapyrrolizidine) in a single molecular framework via three-component 1,3-dipolar cycloaddition reaction of substituted isatin, sarcosine/1,3-thiazoles-4-carboxylic acid and Knoevenagel adduct (2-Cyano-3-phenyl-acrylic acid ethyl ester or 2-Benzylidene-malononitrile) in 2,2,2-trifluoroethanol as a reusable green solvent. Good functional group tolerance and broad scope of usable substrates are other prominent features of the present methodology with high degree of chemo-, regio- and stereoselectivity. The stereochemistry of synthesized compounds was confirmed by single crystal X-ray analysis. All the synthetic compounds were examined for their antimicrobial potential. The synthesized compounds having pyrrolothiazole moiety showed excellent activity against K. pneumoniae as compared to others and even more inhibitory activity than the mentioned drugs, i.e. compounds 6a (MIC=0.09µg/mL), 6b (MIC=0.045µg/mL), 6c (MIC=0.005µg/mL), 6d (MIC=0.19µg/mL). Additionally, compound 6c has shown better binding affinity against New Delhi Metallo-beta-Lactamase-1 (NDM-1) protein in computational docking studies.
