Experimental and theoretical studies on SPION@glutathione catalyzed synthesis of indolyl chromene, indolo xanthene, and pyrimido[4,5-b]quinoline

ABSTRACT

The potential of glutathione as a catalyst for carbon–oxygen ring cyclization was investigated experimentally as well as computationally. The glutathione molecules were immobilized on superparamagnetic iron-oxide nanoparticle so as to improve the efficiency of the catalyst and to augment magnetically aided recyclability. Ultrasound was also exploited for thorough dispersion of the nanoparticles in the aqueous medium so that contact between the catalyst and the reactants are enhanced. This nano-organocatalyst was synthesized and characterized by the following analytical techniques: TEM, scanning electron microscope, EDS, powder X-ray diffraction, vibrating sample magnetometry, FTIR, TGA, DTA. Its catalytic prowess in the synthesis of several indolyl chromenes, pyrrolyl chromenes, and indoloxanthenes were meticulously investigated. The synthetic protocol was found to be efficient, economical, and environment benign. Quantum chemical studies were performed to study the effect of the catalyst on C–O ring cyclization using Gaussian program viz. B3LYP.

GRAPHICAL ABSTRACT

KEYWORDS:

• B3LYP
• indolo-xanthene
• indolyl-chromene
• pyrimido-quinoline
• SPION@glutathione

Acknowledgments

Analytical assistance from SAIF-NEHU, IIT-Guwahati, and the Department of Chemistry-NEHU is highly appreciated. Computational assistance from Computer Centre-NEHU and the PARAM-Sheersh (SULEKOR) supercomputer is acknowledged.

Additional information

Funding

We will also like to thank DST for financial support (sanctioned no: EEQ/2016/000646).