Expedient Access to Alkyne-Tethered N-Acyl Pyrazolines and Pyrazoles From Hydrazides and Skipped Diynones

Abstract

A convenient, catalyst-free protocol for the synthesis of hitherto unknown alkyne-tethered N-acyl pyrazolines from readily available hydrazides and skipped diynones has been developed. The subsequent acid-catalyzed dehydration of the synthesized hydroxy derivatives opened a shortcut toward a representative set of 5-alkynyl-1-acylpyrazoles. The elaborated approaches possess competitive advantages such as complete chemo- and regioselectivity, availability of starting materials and excellent yields (up to quantitative) of target products having rich functionality patterns for further derivatization.