Folded conformations due to arene interactions in dissymmetrical and symmetrical butylidene linker models based on pyrazolo[3,4-d]pyrimidine, purine and 7-deazapurine

Abstract

Abstract Butylidene linker models 1-(2-(2,6-dimethylsulfanyl-9H-purin-9-yl)-2-methylenepropane-4,6-dimethylsulfanyl)-1H-pyrazolo[3,4-d]pyrimidine, (XI), C18H20N8S4, 7,7′-(2-methylenepropane-1,3-diyl)bis(3-methyl-2-methylsulfanyl-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one), (XIV), C20H22N6O2S2 and 7-(2-(4,6-dimethylsulfanyl-1H-pyrazolo[3,4-d]pyrimidin-1-yl)-2-methylenepropane-3-methyl-2-methylsulfanyl-3H-pyrrolo[2,3-d]pyrimidin-4(7H)-one, (XV), C19H21N7OS3 show folded conformations in solution as shown by proton NMR analysis. This folding carries over to solid state for all models as revealed by X-ray crystallography due to intramolecular π‒π interactions. Whereas, only one model (XIV) shows additional intramolecular C‒H…π interactions in solid state. To the best of our knowledge, this is the first report using pyrrolo[2,3-d]pyrimidine nucleus for such kind of study. In addition to the π‒π interactions, crystal structures are also stabilized by other weak intermolecular C‒H…S/N/O and/or S…N/S interactions.