Ultrasound-promoted synthesis of novel bipodal and tripodalpiperidin-4-ones and silica chloride mediated conversion to its piperidin-4-ols: synthesis and structural confinements

Evaluation of xanthene-appended quinoline hybrids as potential leads against antimalarial drug targets

A series of fused heterocycle xanthene-appended quinoline 6a-n was successfully synthesized with regioselectivity and characterized using IR, ¹H NMR, ¹³C NMR, and mass spectral data. Molecular docking was performed to find the binding efficacy of all these newly synthesized compounds towards thirteen antimalarial drug targets. Molecular dynamics simulation was carried out to predict the stability of the ligand-bound complex in a solvent medium. Blind and site-directed docking with compounds 6a-n against 13 drug targets revealed most of the ligands to have a good binding affinity with the targets. Analysis on the basis of binding energy, binding modalities of the ligands, intermolecular interactions, and pharmacophore, we identified only one of the ligand-receptor complexes to provide better results. Molecular dynamic simulation of the selected receptor-ligand complex revealed that the synthesized compound had a better binding affinity with the receptor than the native ligand complex. Further analysis of the synthesized ligand in the laboratory may prove promising results in the search for potential antimalarial drugs.

Hydrogen bonding in 2,6-bis(4-fluorophenyl)-3,5-dimethylpiperidin-4-one methanol solvate

The crystal structure analysis of a 2,6-diaryl 4-piperidone derivative, isolated as a mono-methanol solvate, reveals that both the piperidone and the methanol molecule lie on a crystallographic mirror plane. A chair conformation is found for the piperidone ring with the aryl and methyl groups in equatorial positions. The most prominent feature of the molecular packing is the formation of supramolecular zigzag chains mediated by amine-N–H···O(methanol) and hydroxyl-O–H···N(amine) hydrogen bonds, i.e. the methanol molecule serves as a bridge between piperidone molecules. The molecular structure is compared with that determined in an unsolvated form and the gas-phase equilibrium structure, obtained using density-functional theory (DFT); differences relate, in the main, to the relative dispositions of the aryl rings. An analysis of the Hirshfeld surfaces of the experimental structures indicates very similar relative contributions with the notable exception being the contribution by O···H/H···O which at 13.7% in the methanol solvate is >8.5% in the unsolvated form.

Catalyst-free sonosynthesis of highly substituted propanamide derivatives in water

A clean, rapid and energy-efficient approach to catalyst-free one-pot synthesis of highly substituted propanamide derivatives in water was developed utilizing of the ultrasonic irradiation. The method has been successful in achieving the green chemistry objective. A catalyst-free operation, an energy efficient protocol using ultrasound irradiation instead of conventional heating or stirring and use of water as a non-hazardous, inexpensive and readily available solvent in the one-step reaction against sequential reaction steps thus combining the features of both economic and environmental advantages.

Crystal structures of two chiral piperidine derivatives: 1-[(1R)-2-hy-droxy-1-phenyl-eth-yl]piperidin-4-one and 8-[(1S)-1-phenyl-eth-yl]-1,4-dioxa-8-aza-spiro-[4.5]decane-7-thione

The crystal structures of the two title piperidine derivatives show different conformations for the six-membered heterocycle. The N-substituted 4-piperidinone 1-[(1R)-2-hy-droxy-1-phenyl-eth-yl]piperidin-4-one, C13H17NO2, (I), has a chair conformation, while the piperidine substituted in position 2 with a thio-carbonyl group, 8-[(1S)-1-phenyl-eth-yl]-1,4-dioxa-8-aza-spiro-[4.5]decane-7-thione, C15H19NO2S, (II), features a half-chair conformation. Comparison of the two structures, and data retrieved from the literature, suggests that the conformational flexibility is mainly related to the hybridization state of the C atom α to the piperidinic N atom: a Csp (3) atom favours the chair conformer, while a Csp (2) atom distorts the ring towards a half-chair conformer. In the crystal structure of (I), weak C-H⋯O hydrogen bonds link the mol-ecules into supra-molecular chains propagating along the b-axis direction. In the crystal of (II), the mol-ecules are linked by weak C-H⋯S contacts into supra-molecular chains propagating along the b-axis direction.

Novel, fast and efficient one-pot sonochemical synthesis of 2-aryl-1,3,4-oxadiazoles

Ultrasound promoted synthesis of 2-aryl-1,3,4-oxadiazoles at ambient temperature is reported. The remarkable features of the new procedure are shorter reaction time, excellent yields, cleaner reaction profile and simple experimental and workup procedure.