Conformational Control due to Arene Interactions in Dissymmetrical Diaryl 2-Methylenepropylidene Both in Solution and Solid State

Abstract

We have designed and synthesized dissymmetrical diaryl 2-methylenepropylidenes based on pyrazolo[3,4-d]pyrimidine core for studying conformational control due to arene interactions in face-to-face (offset) mode. Dissymmetrical 2-methylenepropylidene linker models (N1-N1 isomers) show intramolecular π‒π stacking (folded conformation) by 1H NMR in solution which carries over to solid state as revealed by single crystal X-ray crystallography. Corresponding, N1-N2 isomers do not show intramolecular π‒π stacking at molecular level. In addition to arene interactions crystal structures are also stabilized by intermolecular C−H…O, C−H…S or C−H…N interactions.