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The complexes of selected long-chain arylpiperazines with homology models of 5-HT 1A , 5-HT 2A , and 5-HT 7 receptors were investigated using quantum mechanical methods. The molecular geometries of the ligand-receptor complexes were firstly optimized with the Our own N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) method. Next, the fragment molecular orbitals method with an energy decomposition analysis scheme (FMO-EDA) was employed to estimate the interaction energies in binding sites. The results clearly showed that orthosteric binding sites of studied serotonin receptors have both attractive and repulsive regions. In the case of 5-HT 1A and 5-HT 2A two repulsive areas, located in the lower part of the binding pocket, and one large area of attraction engaging many residues at the top of all helices were identified. Additionally, for the 5-HT 7 receptor, the third area of destabilization located at the extracellular end of the helix 6 was found.

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Phase transfer catalysis (PTC) is an excellent possibility in the synthesis of organic compounds as it allows the reactions to be carried out under the conditions of green chemistry, while maintaining high yields and selectivity. The great advantage of these reactions is also the possibility of carrying out the reactions not only under conventional conditions, but also mechanochemically in solvent-free processes. Bearing this in mind, we decided to develop a new method for the synthesis of known biologically active compounds from the group of long-chain arylpiperazines (LCAPs). The first mortar trials were very promising and prompted us to carry out a series of ball mill reactions. One of the technological problems that we encountered while conducting reactions in the ball mill was the difficulty in extracting the post-reaction mixture. We tested the effects of additives improving the insulation of the product, such as, e.g., starch, zeolites, and silica. Research has proven that with appropriate process conditions using TBAB as a catalyst and in the presence of potassium carbonate and a small amount of Zeolite ZSM5 or silica, aripiprazole can be obtained with a yield of 90% in just five minutes. The obtained results are very promising and it is worth considering them as an alternative to the synthesis of other compounds from the LCAPS group.