Base-free efficient palladium catalyst of Heck reaction in molten tetrabutylammonium bromide

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2006-09, Vol.257 (1), p.3-8
• Main Authors: Pryjomska-Ray, Iweta, Trzeciak, Anna M., Ziółkowski, Józef J.
• Format: Article
• Language: English
• Subjects: Base-free Heck reaction; Catalysis; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Heck coupling; Molten tetrabutylammonium salt; Palladium nanoparticles; Phosphorus-free palladium catalyst; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2006.03.064

Phosphine-free palladium precursors (PdCl 2, PdCl 2(PhCN) 2 and Pd(OAc) 2) in molten [ n Bu 4N]Br as the reaction medium and without addition of base were used as components for efficient catalytic systems for Heck coupling of bromobenzene with butyl acrylate. In all the systems under studies the yield of product, butyl cinnamate 1, strongly depends on the concentration of palladium. The maximum yield of 1 was obtained for PdCl 2(PhCN) 2 at 0.09 mol% and for PdCl 2 and Pd(OAc) 2 at ca. 0.4 mol%. Lower yields were obtained below and over that concentration. Addition of bases (NaHCO 3, NaHCO 2, Et 3N or Bu 3N) caused an increase of acrylate conversion and formation of butyl β-phenyl cinnamate 2. During recycling experiments the change of selectivity was observed with increase of 1/ 2 products ratio.