Ruthenium- and rhodium-catalyzed direct carbonylation of the ortho C-H bond in the benzene ring of N-arylpyrazoles

Taku Asaumi; Takuya Matsuo; Takahide Fukuyama; Yutaka Ie; Fumitoshi Kakiuchi; Naoto Chatani

doi:10.1021/jo049864j

Ruthenium- and rhodium-catalyzed direct carbonylation of the ortho C-H bond in the benzene ring of N-arylpyrazoles

J Org Chem. 2004 Jun 25;69(13):4433-40. doi: 10.1021/jo049864j.

Authors

Taku Asaumi¹, Takuya Matsuo, Takahide Fukuyama, Yutaka Ie, Fumitoshi Kakiuchi, Naoto Chatani

Affiliation

¹ Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.

PMID: 15202898
DOI: 10.1021/jo049864j

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.