4.7 Article

Identification of key functionalization species in the Cp☆Ir(III)-catalyzed-ortho halogenation of benzamides

Journal

DALTON TRANSACTIONS
Volume 49, Issue 45, Pages 16166-16174

Publisher

ROYAL SOC CHEMISTRY
DOI: 10.1039/d0dt00565g

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Funding

  1. North Carolina State University
  2. National Science Foundation [CHE-1664973]

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Cp*Ir(iii) complexes have been shown to be effective for the halogenation of N,N-diisopropylbenzamides with N-halosuccinimide as a suitable halogen source. The optimized conditions for the iodination reaction consist of 0.5 mol% [Cp*IrCl2](2) in 1,2-dichloroethane at 60 degrees C for 1 h to form a variety of iodinated benzamides in high yields. Increasing the catalyst loading to 6 mol% and the time to 4 h enabled the bromination reaction of the same substrates. Reactivity was not observed for the chlorination of these substrates. A variety of functional groups on the para-position of the benzamide were well tolerated. Kinetic studies showed the reaction dependence is first order in iridium, positive order in benzamide, and zero order in N-iodosuccinimide. A KIE of 2.5 was obtained from an independent H/D kinetic isotope effect study. Computational studies (DFT-BP3PW91) indicate that a CMD mechanism is more likely than an oxidative addition pathway for the C-H bond activation step. The calculated functionalization step involves an Ir(v) species that is the result of oxidative addition of acetate hypoiodite that is generated in situ from N-iodosuccinimide and acetic acid.

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