title: Ruthenium- and rhodium-catalyzed direct carbonylation of the ortho C-H bond in the benzene ring of N-arylpyrazoles.
abstract: The direct carbonylation of C-H bonds in the benzene ring of N-phenylpyrazoles via catalysis by ruthenium or rhodium complexes is described. The reaction of N-phenylpyrazoles with carbon monoxide and ethylene in the presence of Ru(3)(CO)(12) or Rh(4)(CO)(12) resulted in the site-selective carbonylation of the ortho C-H bonds in the benzene ring to give the corresponding ethyl ketones. A variety of functional groups on the benzene ring can be tolerated. N-Phenylpyrazoles have higher reactivities than would be expected, based on the pK(a) values of the conjugate acid of pyrazole. The choice of solvent for this reaction is significant, and N, N-dimethylacetamide (DMA) gives the best result.
authors.affiliation: Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Asaumi
authors.forename: Takuya
authors.initials: T
authors.lastname: Matsuo
authors.forename: Takahide
authors.initials: T
authors.lastname: Fukuyama
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ie
authors.forename: Fumitoshi
authors.initials: F
authors.lastname: Kakiuchi
authors.forename: Naoto
authors.initials: N
authors.lastname: Chatani