Sustainable Synthetic Approach for (Pyrazol-4-ylidene)pyridines By Metal Catalyst-Free Aerobic C(sp2)–C(sp3) Coupling Reactions between 1‑Amino-2-imino-pyridines and 1‑Aryl-5-pyrazolones

A novel, metal catalyst-free, and efficient method has been developed
for the synthesis of (pyrazol-4-ylidene)­pyridine derivatives. The
process involves dehydrogenative coupling of 1-amino-2-imino-pyridines
with 1-aryl-5-pyrazolone derivatives utilizing O2 as the
sole oxidant. The new method benefits from a high atom economy, efficiency,
and substrate scope, as well as the simplicity of reaction and product
purification procedures.

一种新颖的、无需金属催化剂且高效的合成(吡唑-4-亚甲基)吡啶衍生物的方法已被开发出来。该过程涉及1-氨基-2-亚氨基吡啶与1-芳基-5-吡唑酮衍生物的脱氢偶联反应，其中氧气作为唯一的氧化剂。该方法得益于高原子经济性、高效性、底物适用范围广，以及反应和产物纯化过程的简便性。