Chitosan-bounded copper (chitosan–Cu) was introduced for green synthesis of novel ferrocenated spiropyrrolidine hybrids, namely 3′-(4-.bromobenzoyl)-5′-(4-hydroxybenzyl)-4′-ferrocenylspiro[indoline-3,2′-pyrrolidin]-2-one and 3′-(4-bromobenzoyl)-4′-ferrocenylspiro[indoline-3,2′-pyrrolidin]-2-one, in good yield. A one-pot three-component 1,3-dipolar cycloaddition reaction was employed for the formation of spiropyrrolidines from 1-(4-bromophenyl)-ferrocene-prop-2-en-1-one and azomethine ylides, which were developed in situ from tyrosine, glycine, and isatin, respectively. Various spectroscopic methods were used to establish the structures of spiropyrrolidines, and a single crystal X-ray diffraction study of a spiropyrrolidine provided additional confirmation. The crystallographic study revealed that compound 3a has one independent molecule in its unit cell, which is correlated with Hirshfeld surface analysis, and describes intramolecular contacts adversely. The highly yielded products in green conditions were determined for their antibacterial significance and were found to have good activity against Gram-positive and Gram-negative bacterial strains.

The novel piperidinium dicoumarol has been synthesized by the reaction of 3-formylchromone, 4-hydroxycoumarin, and piperidine under chitosan catalyzed solvent-free green conditions. FT-IR and NMR spectroscopy established the structure of dicoumarol, which was further confirmed by a single X-ray diffraction study. The single diffraction study has revealed the hydrogen bonding interactions, which were further validated by Hirshfeld surface analysis. Geometry optimizations of dicoumarol have been performed at the DFT level of theory by the B3LYP acting along with Gaussian 16, revision B.01 to calculate the geometric and electronic structure parameters.

2-Hydroxy-1-naphthaldehyde based barbiturates were synthesized through an eco-friendly greener approach, by reaction of 2-hydroxynaphthalene-1-carbaldehyde with three different barbituric acid derivatives in presence of natural, biodegradable and biocompatible green catalyst chitosan-SO₃H. The use of solvent-free reaction in presence of functionalized chitosan for the synthesis of barbituric acid derivatives makes the present protocol as green and eco-friendly. A comparative study of conventional as well as solvent-free methods highlights the advantages, such as admirable yield, reduced reaction time with eviction of environmentally hazardous solvents, which leads to sustainability. The chemical structures of compounds were characterized by spectral techniques like IR, ¹H NMR, ¹³C NMR and mass spectrometry. Additionally, computational studies of synthesized compounds were performed using density functional theory (DFT) at M06 level and 6-311 G (d,p) basis set to elucidate the electronic structures, and counter check the experimental findings. Overall, DFT findings at M06/6-311G (d,p) level show good agreement with the experimental data which confirms the purity of entitled compounds. Natural bond orbital (NBO) analysis and non-linear optical (NLO) properties were explored at the M06-/6-311G (d,p) level of theory. NBO analysis confirmed that hyper conjugative interactions are responsible for the stability of compounds. The energy gaps in compounds 5, 6 and 7 were found as 3.822, 3.815 and 3.643 eV, respectively. Furthermore, the global reactivity parameters were calculated using the FMOs energies which indicate that 5–7 hold more donating capability and stability. NLO findings confirmed that 5–7 have superior properties as compared to prototype standard compounds which unveiled their potential applications for optoelectronic technology.