Palladium-catalyzed benzene arylation: incorporation of catalytic pivalic acid as a proton shuttle and a key element in catalyst design.
A palladium-pivalic acid cocatalyst system has been developed that exhibits unprecedented reactivity in direct arylation. This reactivity is illustrated with the first examples of high yielding direct metalation-arylation reactions of a completely unactivated arene, benzene. Experimental and computational evidence indicates that the pivalate anion is a key component in the palladation/C-H bond breaking event, that it lowers the energy of C-H bond cleavage and acts as a catalytic proton shuttle from benzene to the stoichiometric carbonate base. Eight examples of substituted aryl bromides are included which undergo direct arylation with benzene in 55-85% yield.
Lafrance
Marc
M
Center for Catalysis Research and Innovation, University of Ottawa, Department of Chemistry, 10 Marie Curie, Ottawa, Ontario, Canada K1N 6N5.
Fagnou
Keith
K
D000478:Alkylation; D001554:Benzene / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010421:Pentanoic Acids / Q000737:chemistry*; D011522:Protons; D013237:Stereoisomerism
D009942:Organometallic Compounds; D010421:Pentanoic Acids; D011522:Protons; D010165:Palladium; C005566:pivalic acid; D001554:Benzene