Molecular structure of pyrazolo[1,5-a]pyrimidines: X-ray diffractometry and theoretical study

The structure of 7-trichloromethyl-2-methylpyrazolo[1,5-a]pyrimidine (1) and 3-bromo-2-methyl-7-(thien-2-yl)pyrazolo[1,5-a]pyrimidine (2) was determined by X-ray diffractometry. The crystal packing for compounds 1 and 2 was discussed in terms of inter- and intramolecular interactions. Compound 1 showed the intramolecular interaction of pyrazole nitrogen and trichloromethyl chlorine (N⋯Cl), the intermolecular interactions of pyrimidine nitrogen and chlorine (N⋯Cl) and π-π interaction between pyrazole ring-centroid. Compound 2 showed the intramolecular interaction of nitrogen of pyrazole and thienyl sulfur (N⋯S), the intermolecular interactions of nitrogen of pyrimidine and thienyl sulfur (N⋯S) and π-π interaction between pyrimidine and pyrazole ring-centroid. Selected crystallographic data are compared with corresponding semi-empirical AM1 data.