Environmentally-Friendly Synthesis, Structural Determination and Antimicrobial Activity of New Class of Spiropyrrolidine Embedded with Indenoquinoxaline and Chromanone Heterocyclic Units

Abstract

A regio- and stereoselective synthesis of hitherto unexplored novel class of dispiropyrrolidine embedded with indenoquinoxaline and chromanone hybrid heterocycle has been achieved employing an eco-friendly ionic liquid assisted multicomponent 1,3-dipolar cycloaddition cascade protocol. The dipolarophile, 3-(4-methoxybenzylidene)chroman-4-one reacts with non-stabilized 1,3-dipole component derived from indenoquinoxalinone and L-phenylalanine through decarboxylative cascade reaction pathway affording (2 & PRIME;S,4 & PRIME;S)-5 & PRIME;-benzyl-4 & PRIME;(4-methoxyphenyl)dispiro[chromane-3,3 & PRIME;-pyrrolidine-2 & PRIME;,11 & PRIME;'-indeno[1,2-b]quinoxalin]-4-one (6) as the final product. The structure of 6 was confirmed through NMR and mass spectroscopic analyses. Further, stereochemistry of the spirocompound was undoubtedly determined through single crystal XRD analysis. In the crystal structure, the O...H and N...H interactions are the most common contacts and also have great importance in molecular packing. In addition, the C...H contacts are also important in the studied crystal structure. DFT and NBO calculations were performed on this system in order to discuss its electronic and reactivity parameters. The calculated dipole moment value is 2.9238 Debye indicating a polar compound. Compound 6 was assayed for antimicrobial efficacy and found to have potential activity against eight tested microbial pathogens. Among them, E. coli ML_KSUB22 and C. albicans ML_KSUF05 were found to be highly susceptible than the other pathogens.