Ultrasound promoted C–C bond formation: Heck reaction at ambient conditions in room temperature ionic liquids

Abstract

Heck reaction proceeds at ambient temperature (30 degrees C) with considerably enhanced reaction rate (1.5-3 h) through the formation of Pd-biscarbene complexes and stabilized clusters of zero-valent Pd nanoparticles in ionic liquids under ultrasonic irradiation.

Palladium nanoparticle catalysts in ionic liquids: synthesis, characterisation and selective partial hydrogenation of alkynes to Z-alkenes

“…54,55 Therefore, Pd(II)carbene complexes may be formed, most likely by reaction of the imidazolium cation with Pd(0) species. 25,[56][57][58][59] Fig . 3a shows the carbon 1s transition corresponding to the pure (BCN)MI$NTf 2 (dotted line) Pd(OAc) 2 in (BCN)MI$NTf 2 (dashed line) and Pd(0)-NPs in the same IL (solid line).…”

Palladium Nanoscale Catalysts in Ionic Liquids: Coupling and Hydrogenation Reactions

“…Reduction with dihydrogen or hydrides (D-E; X = OAc, halide) or reductive elimination of a palladacycle by reaction with a diene (F). Adapted from references (Takahashi et al, 1970;Reetz & Westermann, 2000;Xu et al, 2000;Deshmukh et al, 2001;Cassol et al, 2005;Umpierre et al, 2005).…”

“…(Hardacre et al, 2003;Dupont, 2004;Gozzo et al, 2004;Tsuzuki et al, 2005) One of the first results reported on the role of ILs in Heck reactions was published by Deshmukh and co-workers in 2001. (Deshmukh et al, 2001) For instance, ILs based on the cation [1,3-di-n-butylimidazolium] and bearing bromide (BBI.Br) and tetrafluoroborate (BBI.BF 4 ) as anions promote a significant improve in the rate of Heck reactions. It was observed that under ultrasonic irradiation and in the presence of base, the C-C couplings of several substituted iodobenzenes and alkenes/alkynes at 30 ºC were performed successfully affording solely the trans-product in high yields (Scheme 4).…”

“…Synthetic approaches using controlled thermal decomposition for the generation of Pd-NPs in ILs use for example: Pd(dba) 2 , (Takahashi et al, 1970) Pd(OAc) 2 or palladium carbene complexes (Scheme 3). (Reetz & Westermann, 2000;Xu et al, 2000;Deshmukh et al, 2001; Furthermore, palladium salts such as PdCl 2 , Na 2 PdCl 4 can be reduced with metal hydrides or simply dihydrogen. Pd-NPs are also formed starting from palladacycles by reaction with dienes (Scheme 3).…”

Ionic Liquid-assisted Solvothermal Synthesis of Ni Particles and Study of Their Electrocatalytic Effect for Calcium Dobesilate Oxidation

“…They have been used in various fields including organic synthesis, catalysis, electrochemistry [25 -27], and inorganic synthesis [28 -30]. The advantages of using RTILs in preparing metallic nanoparticles lies in the facts that they can act as stabilizers for the nanoparticles and are able to isolate metal nanoparticles, making it feasible to prevent the targeted metallic nanoparticles such as gold [31], palladium [32], iridium [33], and germanium [34] from aggregation and hence realize better catalytic function.…”