title: Palladium-catalyzed ortho-arylation of O-phenylcarbamates with simple arenes and sodium persulfate.
abstract: By palladium catalysis, the C-H bond functionalization of O-phenylcarbamates with simple arenes has been achieved using sodium persulfate (Na(2)S(2)O(8)), an inexpensive, easy-to-handle, and environmentally friendly oxidant. This oxidative cross-coupling involves two aromatic C-H bonds undergoing concomitant oxidation to furnish a new biaryl C-C linkage. Excellent reaction efficiencies and regioselectivities were observed with a range of electron-rich, electron-neutral, and electron-deficient arenes; minimal homocoupling of either component was observed. When two reactive C-H bonds are present on the O-phenylcarbamate, selective diarylation can be achieved via quadruple C-H bond functionalization. This work represents a rare example of using O-carbamates as directing groups for catalytic C-H bond activation. Additionally, a palladacycle obtained from an O-phenylcarbamate was prepared and fully characterized. This trifluoroacetate-bridged bimetallic Pd complex exhibits clean conversion to the ortho-arylation product upon treatment with simple arenes. The addition of trifluoroacetic acid (TFA) was found to be critical for successful cyclopalladation of O-phenylcarbamates. We propose this oxidative arene cross-coupling occurs via two discrete C-H bond activations, namely cyclopalladation and electrophilic metalation, within a Pd(0/II) catalytic cycle.
authors.affiliation: Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Zhao
authors.forename: Charles S
authors.initials: CS
authors.lastname: Yeung
authors.forename: Vy M
authors.initials: VM
authors.lastname: Dong
mesh_terms: D002244:Carbon / Q000737:chemistry; D002384:Catalysis; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007454:Iodides / Q000737:chemistry; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation; D010165:Palladium / Q000737:chemistry*; D048448:Phenylcarbamates / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D006841:Hydrocarbons, Aromatic; D007454:Iodides; D048448:Phenylcarbamates; D017670:Sodium Compounds; D013431:Sulfates; D010165:Palladium; D002244:Carbon; D006859:Hydrogen; D014269:Trifluoroacetic Acid; C024625:sodium persulfate