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

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2014-06, Vol.70 (6), p.555-561
• Main Authors: Avasthi, Kamlakar, Shukla, Lakshmi, Kant, Ruchir, Ravikumar, Krishnan
• Format: Article
• Language: English
• Subjects: 7‐deazapurine; arene interactions; Aromatic compounds; butylidene linker; Chemical bonds; Chemical compounds; Crystal structure; Crystallography; Crystallography, X-Ray; folded conformations; Folding; Hydrogen Bonding; Magnetic Resonance Spectroscopy; Mathematical models; Molecular Conformation; Molecules; Nuclei; purine; Purines; Purines - chemistry; Pyrazoles - chemistry; pyrazolo[3,4‐d]pyrimidine; Pyrimidines - chemistry; Pyrroles - chemistry; Solid state; Symmetry
• ISSN: 2053-2296; 0108-2701; 2053-2296; 1600-5759
• DOI: 10.1107/S2053229614009449

The butylidene‐linker models 1‐[2‐(2,6‐dimethylsulfanyl‐9H‐purin‐9‐yl)‐2‐methylidenepropyl]‐4,6‐bis(methylsulfanyl)‐1H‐pyrazolo[3,4‐d]pyrimidine, C18H20N8S4, (XI), 7,7′‐(2‐methylidenepropane‐1,3‐diyl)bis[3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one], C20H22N6O2S2, (XIV), and 7‐[2‐(4,6‐dimethylsulfanyl‐1H‐pyrazolo[3,4‐d]pyrimidin‐1‐yl)‐2‐methylidenepropyl]‐3‐methyl‐2‐methylsulfanyl‐3H‐pyrrolo[2,3‐d]pyrimidin‐4(7H)‐one, C19H21N7OS3, (XV), show folded conformations in solution, as shown by 1H NMR analysis. This folding carries over to the crystalline state. Intramolecular π–π interactions are observed in all three compounds, but only (XIV) shows additional intramolecular C—H...π interactions in the solid state. As far as can be established, this is the first report incorporating the pyrrolo[2,3‐d]pyrimidine nucleus for such a study. In addition to the π–π interactions, the crystal structures are also stabilized by other weak intermolecular C—H...S/N/O and/or S...N/S interactions.