Hydrogen-bonded chains in isostruo tural 5-methyl-2-(4-methylphenyl)7,8- dihydro-6H-cyclopenta[g]pyrazolo[1,5-a]pyrimidine, 2-(4-chloro-phenyl)-5-methyl- 7,8-dihydro-6H-cyclopenta[g]pyrazolo[1,5-a]pyrimidine and 2-(4-bromophenyl)-5- methyl-7,8-dihydro-6H-cyclopenta[g]pyrazolo1,5/a-alpyrimidine

Abstract

5-Methyl-2-(4-methylphenyl)-7,8-dihydro-6H-cyclopenta[g]-pyrazolo[l,5-a] pyrimidine, C17H17N3, 2-(4-chlorophenyl)-5- methyl-7,8-dihydro-6H-cyclopenta[g]pyrazolo[1,5-fl]pyrimidine, C 16H14ClN3, and 2-(4-bromophenyl)-5-methyl-7,8- dihydro-6H-cyclopenta[g]pyrazolo[1,5-a]pyrimidine, C16H 14BrN3, are isostructural; in each compound, the molecules are linked into chains by a single C-H⋯π(arene) hydrogen bond. Molecules of 2-(4-methoxyphenyl)-5-methyl-7,8-dihydro-6H-cyclopenta[g] pyrazolo[1,5-a]pyrimidine, C17H17N3O, are linked by a single C-H⋯N hydrogen bond into chains, which are themselves linked into sheets by a π-π stacking interaction. © 2005 International Union of Crystallography.