To a solution of 7-chloro-5-(4-chloro-phenyl)-pyrazolo[1,5-a]pyrimidine (2.1 g, 8.0 mmol) and tetrakis(triphenylphosphine)palladium (0.92 g, 0.8 mmol) in THF (14 mL) was added at 20° C. 0.25 M cyclopropylzinc chloride/THF suspension (ca. 128 mL, 32 mmol; freshly prepared by stirring a mixture of 64 mL of 0.5 M cyclopropylmagnesium bromide/THF and 64 mL of 0.5 M zinc chloride/THF for 1 h at 0° C., followed by 1 h at 20° C.) and the mixture was refluxed in an atmosphere of argon for 1.5 h. After the slow addition at 0° C. of saturated aqueous NH4Cl solution (20 mL), the mixture was partitioned between EtOAc and 10% sodium chloride solution. The organic layer was dried (Na2SO4) and evaporated in vacuo. The residue was chromatographed on silica gel using EtOAc/hexane (1:5 v/v) as eluent to give 5-(4-chloro-phenyl)-7-cyclopropyl-pyrazolo-[1,5-a]pyrimidine (1.50 g, 69%) as an off-white solid. MS (ISP) 270.4 [(M+H)+]; mp 137-138° C.
