Dimethylformamide → 4-Fluoro-2,6-dimethoxybenzaldehyde

Participants

Reaction Steps

A cooled (−5° C.) mixture of commercially available 1-fluoro-3,5-dimethoxybenzene (500 mg; 3.20 mmol; 1.0 equiv.) and DMF (4.680 g; 64.03 mmol; 20.0 equiv.) was treated dropwise with POCl3 (2.454 g; 16.01 mmol; 5.0 equiv.). This mixture was further stirred at rt for 1.5 h, and was then heated to 60° C. for 3 h. After cooling to rt, ice-water (50 ml) and a solution of 2.5 M aq. NaOH (24 ml) were successively added. After extractions with AcOEt (3×30 ml), the mixed organic layers were dried over anh. MgSO4, filtered, and concentrated to dryness under reduced pressure. Purification by FC (heptane/AcOEt=1/1) afforded 4-fluoro-2,6-dimethoxybenzaldehyde as a yellow solid. LC-MS (conditions A): tR=0.50 min.; [M+H]+: 185.10 g/mol. According to 1H-NMR (CDCl3; 400 MHz), this product also contained 19% of the regioisomer 2-fluoro-4,6-dimethoxybenzaldehyde. This minor regioisomer could be advantageously removed after further chemical transformations of the isomeric mixture.

Provenance & Evidence