One-flask synthesis of pyrazolone thioethers involving catalyzed and uncatalyzed thioetherification pathways of pyrazolones

Abstract

A one-flask thioetherification of pyrazolones has been demonstrated by transforming several pyrazolones to their corresponding 4-mercaptopyrazolone derivatives and employing them towards cross-coupling with various aromatic and heteroaromatic iodides by applying Pd(OAc)₂/xantphos as the catalytic system. The coupling ability of these thiol intermediates with 2,3-dichloropyrazine through an aromatic S_N2 pathway has also been established. This methodology provides the use of inexpensive starting materials along with a short reaction time.