Unusual molecular conformation in dissymmetric propylene-linker compounds containing pyrazolo[3,4-d]pyrimidine and phthalimide moieties.

The crystal structure of 4,6-bis(methylsulfanyl)-1-phthalimidopropyl-1H-pyrazolo[3,4-d]pyrimidine, C(18)H(17)N(5)O(2)S(2), (VI), reveals an unusual folded conformation due to an apparent intramolecular C-H.pi interaction between the 6-methylsulfanyl and phenyl groups. However, the closely related compound 6-methylsulfanyl-1-phthalimidopropyl-4-(pyrrolidin-1-yl)-1H-pyrazolo[3,4-d]pyrimidine, C(21)H(22)N(6)O(2)S, (VII), exhibits a fully extended structure, devoid of any intramolecular C-H.pi or pi-pi interactions. The crystal packing of both molecules involves intermolecular stacking interactions due to aromatic pi-pi interactions. In addition, (VI) exhibits intermolecular C-H.O hydrogen bonding and (VII) exhibits dimerization of the molecules through intermolecular C-H.N hydrogen bonding.