Generation of Bis(pentafluorophenyl)boron Enolates from Alkynes and Their Catalyst‐Free Alkyne Coupling

Abstract

Carbon‐carbon bond forming reactions are powerful synthetic tools for constructing organic molecular frameworks. In this study, strongly Lewis acidic bis(pentafluorophenyl)boron enolates were generated from alkynes through oxygen transfer from 2,6‐dibromopyridine N‐oxide using tris(pentafluorophenyl)borane [B(C6F5)3]. Boron enolates were highly reactive owing to the strong acidity of the boron centers, and thus immediately coupled with alkynes. N‐Ethynylphthalimide reacted as an alkyne with 2,6‐dibromopyridine N‐oxide and B(C6F5)3 to form a semi‐stable bis(pentafluorophenyl)boron enolate through the coordination of the carbonyl group to the boron center. This enolate underwent coupling with another alkyne.