By condensation of 2,4-dichlorobenzoic acid (I) with anthranilic acid (II) by means of K2CO3, powdered Cu and a small amount of I2 in refluxing isoamyl alcohol.
Condensation of 2-acetylthiophene (I) with dimethylformamide dimethylacetal produced enaminone (II), which was subsequently cyclized to the isoxazole (III) upon treatment with hydroxylamine. Further condensation of (III) with dimethylformamide dimethylacetal, with concomitant isoxazole ring opening, gave rise to the enamino nitrile (IV). This was then cyclized with aminoguanidine nitrate (V) under basic conditions to furnish the intermediate aminopyrazole (VI).
3-(Acetamido)acetophenone (VII) was converted to enaminone (VIII) upon condensation with dimethylformamide dimethylacetal. The amide N of (VIII) was then alkylated by means of iodomethane and NaH or, alternatively, under phase-transfer conditions to give (IX). Finally, condensation between enaminone (IX) and aminopyrazole (VI) in refluxing AcOH provided the target pyrazolopyrimidine.