Mild Aliphatic and Benzylic Hydrocarbon C-H Bond Chlorination Using Trichloroisocyanuric Acid

J Org Chem. 2017 Mar 3;82(5):2407-2413. doi: 10.1021/acs.joc.6b02829. Epub 2017 Feb 10.

Abstract

We present the controlled monochlorination of aliphatic and benzylic hydrocarbons with only 1 equiv of substrate at 25-30 °C using N-hydroxyphthalimide (NHPI) as radical initiator and commercially available trichloroisocyanuric acid (TCCA) as the chlorine source. Catalytic amounts of CBr4 reduced the reaction times considerably due to the formation of chain-carrying ·CBr3 radicals. Benzylic C-H chlorination affords moderate to good yields for arenes carrying electron-withdrawing (50-85%) or weakly electron-donating groups (31-73%); cyclic aliphatic substrates provide low yields (24-38%). The products could be synthesized on a gram scale followed by simple purification via distillation. We report the first direct side-chain chlorination of 3-methylbenzoate affording methyl 3-(chloromethyl)benzoate, which is an important building block for the synthesis of vasodilator taprostene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon-13 Magnetic Resonance Spectroscopy
  • Chlorine / chemistry*
  • Hydrocarbons / chemistry*
  • Proton Magnetic Resonance Spectroscopy
  • Triazines / chemistry*

Substances

  • Hydrocarbons
  • Triazines
  • trichloroisocyanuric acid
  • Chlorine