Synthesis
The general procedure for the synthesis of 6-chlorosalicylaldehyde from 2-chloro-6-fluoro-benzaldehyde was as follows: potassium hydroxide (10 g) was slowly added to a stirred solution of 2-chloro-6-fluoro-benzaldehyde (14.0 g, 88.3 mmol) in dimethyl sulfoxide (20 mL) at 0 °C. Subsequently, the reaction mixture was gradually warmed to room temperature and stirred continuously for 18 hours. Upon completion of the reaction, the reaction mixture was diluted with 100 mL of water and the pH was adjusted with concentrated hydrochloric acid to 2. The precipitate was collected by filtration, washed twice successively with 100 mL of water, and then dried with anhydrous sodium sulfate to afford the crude product, which was used in the subsequent reaction without further purification. The final yield was 8.5 g in 62% yield. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3) with δppm 6.65-7.02 (m, 2H), 7.39-7.47 (m, 1H), 10.41 (s, 1H), 11.95 (s, 1H).
References
[1] European Journal of Organic Chemistry, 2018, vol. 2018, # 25, p. 3348 - 3351
[2] Patent: WO2012/87229, 2012, A1. Location in patent: Page/Page column 14
[3] Patent: US2008/171754, 2008, A1. Location in patent: Page/Page column 89
[4] Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry (1972-1999), 1993, # 12, p. 1345 - 1358
[5] Zeitschrift fuer Naturforschung, Teil B: Anorganische Chemie, Organische Chemie, Biochemie, Biophysik, Biologie, 1972, vol. 27, p. 663 - 674
