Palladium-Catalyzed C−C Coupling under Thermomorphic Conditions
摘要:
Liquid-liquid biphasic systems that exhibit an increase in phase miscibility at elevated temperature together with soluble polymer-bound catalysts that have a strong phase preference at ambient temperature are described. In such systems, product isolation and catalyst recovery are effected by a liquid/liquid separation. This report-describes the use of such thermomorphic catalyst recovery systems for palladium-catalyzed carbon-carbon bond forming reactions. Poly(N-isopropylacrylamide) (PNIPAM)-bound phosphine ligands with a Pd(0) catalyst used previously in allylic substitution chemistry are efficient catalysts in Heck, Suzuki, and sp-sp(2) cross-coupling reactions. Air-stable tridentate SCS-Pd(II) catalysts bound to PNIPAM or poly(ethylene glycol) (PEG) are also described. A particular advantage of these SCS catalysts is that no precautions against adventitious catalyst oxidation need be taken with the polymer-bound SCS-PdCl catalysts; thus avoiding time-consuming solvent purification and degassing protocols.
Tridentate SCS Palladium(II) Complexes: New, Highly Stable, Recyclable Catalysts for the Heck Reaction
作者:David E. Bergbreiter、Philip L. Osburn、Yun-Shan Liu
DOI:10.1021/ja991099g
日期:1999.10.1
A new pincer-type SCS ligand containing Pd(II) is a simple, robust catalyst for Heck chemistry using a variety of alkene acceptors and aryl iodides. It is less active with aryl bromides. While certain palladium(II) species insert slowly into the aryl C−H bond of an unsubstituted version of this ligand, the introduction of activating groups into the 5 position of the aromatic ring readily allows quantitative
Preparation of Tethered Palladium Catalysis Supported on Gold(111) and Its Surface Characterization by X-ray Photoelectron Spectroscopy (XPS)
作者:Rabbani M. Gulam、Masahiro Hamada、Ikuko Takamiya、Masahiko Shimoda、Satoshi Shuto、Atsushi Nishida、Shiro Tsukamoto、Mitsuhiro Arisawa
DOI:10.1246/bcsj.81.1012
日期:2008.8.15
the confinement of the ligands was confirmed by X-rayphotoelectronspectroscopy (XPS). Palladium was anchored to the ligands to construct heterogeneous Pd}-L-Au(11) catalysts (L = ligand). A Pd}-Au(11) catalyst was also prepared by adsorbing the Pd complex directly on the Au(lll) substrate without a tethering ligand. Both types of catalysts were used in the Mizoroki-Heck reaction to evaluate their
Palladium-Catalyzed C−C Coupling under Thermomorphic Conditions
作者:David E. Bergbreiter、Philip L. Osburn、Allan Wilson、Erin M. Sink
DOI:10.1021/ja001708g
日期:2000.9.1
Liquid-liquid biphasic systems that exhibit an increase in phase miscibility at elevated temperature together with soluble polymer-bound catalysts that have a strong phase preference at ambient temperature are described. In such systems, product isolation and catalyst recovery are effected by a liquid/liquid separation. This report-describes the use of such thermomorphic catalyst recovery systems for palladium-catalyzed carbon-carbon bond forming reactions. Poly(N-isopropylacrylamide) (PNIPAM)-bound phosphine ligands with a Pd(0) catalyst used previously in allylic substitution chemistry are efficient catalysts in Heck, Suzuki, and sp-sp(2) cross-coupling reactions. Air-stable tridentate SCS-Pd(II) catalysts bound to PNIPAM or poly(ethylene glycol) (PEG) are also described. A particular advantage of these SCS catalysts is that no precautions against adventitious catalyst oxidation need be taken with the polymer-bound SCS-PdCl catalysts; thus avoiding time-consuming solvent purification and degassing protocols.
Evidence that SCS Pincer Pd(II) Complexes are only Precatalysts in Heck Catalysis and the Implications for Catalyst Recovery and Reuse
作者:Kunquan Yu、William Sommer、John?M. Richardson、Marcus Weck、Christopher?W. Jones
DOI:10.1002/adsc.200404264
日期:2005.1
SCS-pincer Pd(II) complexes have been covalently immobilized onto porous silica, cross-linked polymer (Merrifield resin) and soluble poly(norbornene) supports via either amide or urea linkages and evaluated in the Heck coupling of iodobenzene with n-butyl acrylate. Kinetic experiments and poisoning studies indicate that in all cases the pincer complexes merely act as precatalysts. Contrary to literature