844648-22-2

5,7-Difluorochroman-4-one is used as a reagent in the prepaation of tetrazolinone compounds,used as pest control agents.

At 50 °C, 3-(3,5-difluorophenoxy)propionic acid (20.0 g, 99 mmol) was added to 60 mL of concentrated sulfuric acid in batches and stirred until completely dissolved. The resulting yellow-green solution was stirred continuously at 50 °C for 1.5 hours. Upon completion of the reaction, the mixture was cooled to room temperature and slowly poured into 800 mL of ice water. After standing for 1 hour, the colorless precipitate was collected by filtration and washed well with cold water. The resulting 5,7-difluorobenzodihydropyran-4-one was dried over phosphorus pentoxide to give 15.69 g of colorless solid in 86% yield.

[1] Patent: WO2008/151927, 2008, A2. Location in patent: Page/Page column 61
[2] Patent: KR2018/11830, 2018, A. Location in patent: Paragraph 0061; 0076; 0077
[3] Patent: US2005/38032, 2005, A1. Location in patent: Page/Page column 31