In this thesis, the synthesis of heterocyclic compounds were performed using cheap and biodegradable deep eutectic solvents (DESs). One-pot multi-component reactions, due to the one-pot formation of C-C and C-X bonds, simple and mild reaction conditions, energy saving and environmental compatibility have been the subject of interest in carbon-carbon and carbon-heteroatom bond formation. Therefore, in the first part of this study, the use of catalytic application of choline chloride/tin chloride deep eutectic solvent has been studied in the synthesis of quinoline derivatives. In this section, different (16) quinoline derivatives were synthesized simply at 60?C in 2-3 hours with 54-97% yields with using choline chloride/tin chloride. After purification, the structure of compounds was identified and confirmed. Moreover the recover ability of the employed catalysts in these syntheses was investigated. Then, in order to develop one-pot multi-component reactions in a green media, the coated iron-based magnetic nanocatalyst was used in the synthesis of xanthene and 2-amino-4H-pyran derivatives. Various (19) xanthene derivatives were synthesized at 90?C in 30 minutes with 56-96% yields with using choline chloride/tin chloride or Fe 3 O 4 /?-Carrageenan/Zn(II). In addition, various (11) 2-amino-4H-pyran derivatives were synthesized at 25?C in 10 minutes with 46-95% yields using Fe 3 O 4 /EDTA nano magnetic catalyst. Verification of the structures of all products in the experimental section was conducted using mp, FT-IR, 1 H-NMR and 13 C-NMR spectra and compare them with reports. In the first part of theoretical studies, adsorption of rare gases into and on the surface of sulfur doped carbon nanotube was studied using DFT, QTAIM and NBO calculations. The structures were optimized in the gas phase and solvents (benzene, cyclohexane and acetone) using PCM method and SCRF keyword. Calculations were performed using CAM-B3LYP method and 6-31G, 6-31G(d) and 6-311+G(d) basis sets for structures. The calculated adsorption energy values showed that He and then Ar are the best rare gases for adsorption by sulfur doped carbon nanotubes. In the second part, the adsorption of Fluoxetine into and on the surface of simple and sulfur doped carbon nanotubes was studied using theoretical calculations. Therefore, the structures were optimized in the gas phase and solvents (water and dimethyl sulfoxide) using DFT method. All optimizations were performed using B3LYP method with the 3-21G and 6-31G basis sets and the energy calculations were done using ?B97XD method and 6-31G basis set. Then, to study of the larger and more reliable models of nanotubes and study of their double (DW) and triple (TW) walled models, the molecular docking calculations were used. As a result, the most negative adsorption energies for Fluoxetine was found when it adsorbed into DW and TW carbon nanotubes with (8,8) chirality. In the final section, the potentials of aluminum doped graphene as a catalyst for conversion of methanol to gasoline process was studies. In this part, the optimizations of all structures were performed using M062X/6-31G and the frequency calculations were done using M062X/6-311G(d) level of theory. The geometry optimization of the transition states was performed using Schlegel’s synchronous transit-guided quasi-Newton (QST3) method. The structures of transition states were confirmed by observing one negative frequency. In addition, the reaction path was confirmed using intrinsic reaction coordinate (IRC) calculations. As a result, it was concluded that due to the exothermic natures of all steps for conversion of methanol to gasoline process, aluminum doped graphene could be used as a catalyst of this reaction.