Organocatalytic Dearomatization of 5-Aminopyrazoles: Synthesis of 4-Hydroxypyrazolines

Dearomatization is a fundamental chemical reaction that affords complex three-dimensional heterocyclic frameworks. We disclose the first organocatalytic dearomatization of 5-aminopyrazoles, which yields a range of structurally diversified C4-hydroxylated pyrazolines with yields of ≤95% in <1.5 h at room temperature. This catalytic process is achieved using