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

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.