title: Improved synthetic route to quinoxyfen photometabolite 2-chloro-10-fluorochromeno[2,3,4-de]quinoline.
abstract: BACKGROUND
  Quinoxyfen is a fungicide developed by Dow AgroSciences for the control of powdery mildew. Re-registration studies required gram quantities of 2-chloro-10-fluorochromeno[2,3,4-de]quinoline, a photometabolite of quinoxyfen. The only previous method of preparation of this photometabolite was by photolysis of quinoxyfen in less than 1% yield. Therefore, a new method allowing for the preparation of this photometabolite in gram quantities was required.
  
  
  RESULTS
  Several different metal catalyzed intramolecular cyclization approaches were investigated for the synthesis of 2-chloro-10-fluorochromeno[2,3,4-de]quinoline. While most methods failed to provide the desired product from a 2-bromophenyl derivative of quinoxyfen, a novel one-pot two-step synthesis led to the desired material in good yield from quinoxyfen.
  
  
  CONCLUSIONS
  A short and efficient synthetic route was developed to access 2-chloro-10-fluorochromeno[2,3,4-de]quinoline from readily available (4-fluoro-2-hydroxyphenyl)boronic acid and quinoxyfen and was found to be scalable, which enabled the preparation of the desired photometabolite in gram quantities thus meeting material requirements to complete regulatory studies for the re-registration of quinoxyfen. © 2017 Society of Chemical Industry.
authors.affiliation: R&D Dow Agrosciences, 9330 Zionsville Road, Indianapolis, IN, USA.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Johnson
authors.affiliation: R&D Dow Agrosciences, 9330 Zionsville Road, Indianapolis, IN, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Kister
authors.affiliation: R&D Dow Agrosciences, 9330 Zionsville Road, Indianapolis, IN, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Thornburgh
mesh_terms: D060326:Chemistry Techniques, Synthetic / Q000379:methods*; D005659:Fungicides, Industrial / Q000378:metabolism*; D008027:Light; D011804:Quinolines / Q000138:chemical synthesis* / Q000378:metabolism*
chemical_list: C000626238:2-chloro-10-fluorochromeno(2,3,4-de)quinoline; D005659:Fungicides, Industrial; D011804:Quinolines; C470613:quinoxyfen
keywords: 2-chloro-10-fluorochromeno[2,3,4-de]quinoline; fungicide photolysis; photometabolite; quinoxyfen