Two new syntheses of a 4-aminopyrazole: Condensation of an N-substituted vinamidinium salt with a functionalized hydrazine

Two novel syntheses of a key 4-aminopyrazole synthetic building block are described. Both routes avoid the potentially explosive precursors that were used in the previously patented route. A salt of a vinamidinium cation previously used in 5-aminopyrimidine synthesis was condensed with a protected hydrazine salt leading to a 4-aminopyrazole. Buchwald-type amination coupling has also been shown to yield the same compound.