Preparation of 3,4-Substituted-5-Aminopyrazoles and 4‑Substituted-2-Aminothiazoles

3,4-Substituted-5-aminopyrazoles
and 4-substituted-2-aminothiazoles
are frequently used intermediates in medicinal chemistry and drug
discovery projects. We report an expedient flexible synthesis of 3,4-substituted-5-aminopyrazoles
(35 examples), based on palladium-mediated α-arylation of β-ketonitriles
with aryl bromides. A library of 4-substituted-2-aminothiazoles (21
examples) was assembled by a sequence employing Suzuki coupling of
newly prepared, properly protected pinacol ester and MIDA ester of
4-boronic acid-2-aminothiazole with (hetero)­aryl halides.