Solid state bromination of a number of substituted phenol, aniline and nitro aromatic compounds with N-bromosuccinimide yields exclusively the nuclear brominated products. Reactivity in the solid state depends on the reaction time, temperature and nature of the substituent on the substrate. The reaction apparently proceeds by an electrophilic aromatic substitution pathway. Molecular orbital and reaction free energy calculations also support such a view. Thermal analysis and video microscopic observation reveal the nature of the solid state reaction. Crystallinity is required for the reactivity and product selectivity. Product yield decreases with loss of selectivity when the reaction is carried out in a melt or in solution. Unlike the topochemical solid state reactions wherein molecular packing is more important than the intrinsic reactivity, these reactions demonstrate the importance of both these factors.

Comparative molecular field analysis and comparative molecular similarity indices analysis were performed on 114 analogues of 1,2-diarylimidazole to optimize their cyclooxygenase-2 (COX-2) selective antiinflammatory activities. These studies produced models with high correlation coefficients and good predictive abilities. Docking studies were also carried out wherein these analogues were docked into the active sites of both COX-1 and COX-2 to analyze the receptor ligand interactions that confer selectivity for COX-2. The most active molecule in the series (53) adopts an orientation similar to that of SC-558 (4-[5-(4-bromophenyl)-3-trifluoromethyl-1H-1-pyrozolyl]-1-benzenesulfonamide) inside the COX-2 active site while the least active molecule (101) optimizes in a different orientation. In the active site, there are some strong hydrogen-bonding interactions observed between residues His90, Arg513, and Phe518 and the ligands. Additionally, a correlation of the quantitative structure-activity relationship data and the docking results is found to validate each other and suggests the importance of the binding step in overall drug action.

No abstract