Effect of imidazolinium salts bearing hydroxy substituents on palladium-catalysed Suzuki–Miyaura and Heck coupling reactions

Abstract

Palladium anionic complexes with imidazolinium cations containing hydroxyl substituents were used as catalyst precursors in the Suzuki-Miyaura and the Heck cross-coupling.High activity of anionic complexes was noted in the Suzuki-Miyaura reaction of 2-bromotoluene with phenylboronic acid at 40 o C in 2-propanol and a 2-propanol/water mixture using conventional heating or microwaves. Similarly, bromonaphtalene and iodonaphtalene reacted efficiently with naphtylboronic acid and 4-methylnaphtylboronic acid. A remarkably lower activity was noted when anionic palladium complexes were employed in the Heck coupling of 2,3-dihydrofuran withiodobenzene. An increase in conversion in the Heck reaction was achieved when Pd(OAc)2 was used as a catalyst precursor together with imidazolinium salts as co-catalysts. ________________________________________________________________________________

The Mizoroki‐Heck Reaction in Tunable Aryl Alkyl Ionic Liquids

“…[31][32][33][34][35][36] Richard F. Heck was, together with Eiichi Negishi and Akira Suzuki, awarded with the 2010 Nobel prize in chemistry for their work on transition metal catalyzed cross-coupling reactions. [37,38] As solvents for the Mizoroki-Heck reaction, a variety of ionic liquids e. g. ammonium, [39][40][41][42] imidazolium, [43][44][45][46][47] pyridinium, [48] and phosphonium [49] based ILs have been used. In this work, we describe the use of tunable aryl alkyl ionic liquids (TAAILs) as solvents in the Mizoroki-Heck reaction.…”