An efficient synthesis of a dual PPAR alpha/gamma agonist and the formation of a sterically congested alpha-aryloxyisobutyric acid via a Bargellini reaction

J Org Chem. 2005 Oct 14;70(21):8560-3. doi: 10.1021/jo051027+.

Abstract

A practical synthesis of benzisoxazole 1 and its conversion to alpha-aryloxyisobutyric acid 2 using 1,1,1-trichloro-2-methyl-2-propanol (chloretone) was developed. Benzisoxazole 1 was formed in high yields by the action of either methanesulfonyl chloride/base upon intermediate oxime 8 or with thionyl chloride/base, which initially forms cyclic sulfite 10. A highly reactive, short-lived intermediate derived from chloretone was detected by ReacIR and its half-life determined to be approximately 5 min. Reaction conditions for the Bargellini reaction were developed that resulted in a 95% yield of 2 from the reaction of highly hindered phenol 1 with chloretone hemihydrate and powdered NaOH in acetone. Thus highly hindered alpha-aryloxyisobutyric acids can be made in a single step in high yield.

MeSH terms

  • Butyrates / chemical synthesis*
  • Butyrates / chemistry
  • Isoxazoles / chemical synthesis*
  • Isoxazoles / chemistry
  • Molecular Structure
  • PPAR alpha / agonists*
  • PPAR gamma / agonists*
  • Propionates / chemical synthesis*
  • Propionates / chemistry

Substances

  • Butyrates
  • Isoxazoles
  • PPAR alpha
  • PPAR gamma
  • Propionates
  • 2-((5,7-dipropyl-3-(trifluoromethyl)-1,2-benzisoxazol-6-yl)oxy)-2-methylpropanoic acid