BF₃‧OEt₂ promoted synthesis of 9-fluorenlidene appended 2-hydrazinopyridine imines from (phenylethynyl)-fluorene and 2-hydrazinopyridine derivatives

Abstract

Reaction of 9-fluorene propargylic alcohols and substituted-2-hydrazinopyridine using BF₃·OEt₂ as a Lewis acid catalyst afforded 9-fluorenlidene appended 2-hydrazinopyridine imine derivatives has been developed. The scope of the reaction is demonstrated by selecting a range of fluorene propargylic alcohols and substituted 2-hydrazinopyridine imines. All the synthesized molecules were characterized using various spectroscopic and analytical techniques including ¹H NMR,¹³C NMR, and Mass spectrometry. A plausible reaction mechanism for forming title compounds via propargylic allenyl carbocation is postulated. The synthetic utility of products thus formed is demonstrated by utilizing Suzuki coupling.

Graphical Abstract

Keywords:

• Fluorene propargylic alcohols
• 2-hydrazinopyridine
• 2-hydrazinopyridine imines
• BF₃·OEt₂
• Suzuki reaction

Acknowledgments

P. S. thanks the Director, CSIR-CLRI for providing infrastructure facilities. The authors thank VIT-Vellore for HRMS data. This research work was carried out by S.S.S as a part of a Ph.D. degree registered at the University of Madras.

Disclosure statement

No potential conflict of interest was reported by the author(s).