Vilsmeier−Haack Reaction of 1-Cyclopropyl-2-arylethanones

A convenient and efficient method to synthesize 3-(2-chloroethyl)-5-aryl-4H-pyran-4-ones 2 and 2-chloro-3-(2-chloroethyl)-1-naphthaldehydes 3 in moderate to good yields was developed via the Vilsmeier−Haack reaction of readily available 1-cyclopropyl-2-arylethanones 1 at different temperature. This reaction proceeds via sequential enolization, ring opening, haloformylation, and intramolecular nucleophilic cyclization or Friedel−Crafts alkylation reactions to produce 2 or 3.