title: Self-assembled poly(imidazole-palladium): highly active, reusable catalyst at parts per million to parts per billion levels.
abstract: Metalloenzymes are essential proteins with vital activity that promote high-efficiency enzymatic reactions. To ensure catalytic activity, stability, and reusability for safe, nontoxic, sustainable chemistry, and green organic synthesis, it is important to develop metalloenzyme-inspired polymer-supported metal catalysts. Here, we present a highly active, reusable, self-assembled catalyst of poly(imidazole-acrylamide) and palladium species inspired by metalloenzymes and apply our convolution methodology to the preparation of polymeric metal catalysts. Thus, a metalloenzyme-inspired polymeric imidazole Pd catalyst (MEPI-Pd) was readily prepared by the coordinative convolution of (NH(4))(2)PdCl(4) and poly[(N-vinylimidazole)-co-(N-isopropylacrylamide)(5)] in a methanol-water solution at 80 °C for 30 min. SEM observation revealed that MEPI-Pd has a globular-aggregated, self-assembled structure. TEM observation and XPS and EDX analyses indicated that PdCl(2) and Pd(0) nanoparticles were uniformly dispersed in MEPI-Pd. MEPI-Pd was utilized for the allylic arylation/alkenylation/vinylation of allylic esters and carbonates with aryl/alkenylboronic acids, vinylboronic acid esters, and tetraaryl borates. Even 0.8-40 mol ppm Pd of MEPI-Pd efficiently promoted allylic arylation/alkenylation/vinylation in alcohol and/or water with a catalytic turnover number (TON) of 20,000-1,250,000. Furthermore, MEPI-Pd efficiently promoted the Suzuki-Miyaura reaction of a variety of inactivated aryl chlorides as well as aryl bromides and iodides in water with a TON of up to 3,570,000. MEPI-Pd was reused for the allylic arylation and Suzuki-Miyaura reaction of an aryl chloride without loss of catalytic activity.
authors.affiliation: RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan. ymayamada@riken.jp
authors.forename: Yoichi M A
authors.initials: YM
authors.lastname: Yamada
authors.forename: Shaheen M
authors.initials: SM
authors.lastname: Sarkar
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Uozumi
mesh_terms: D001897:Boronic Acids / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods; D004952:Esters / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008956:Models, Chemical; D010165:Palladium / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
chemical_list: D001897:Boronic Acids; D004952:Esters; D007093:Imidazoles; D011108:Polymers; D010165:Palladium; D002244:Carbon; C425704:N-vinylimidazole