General procedure for the synthesis of 3,5-dimethyl-4-isoxazole formaldehyde from 3,5-dimethyl-4-hydroxymethylisoxazole: To a solution of (3,5-dimethylisoxazol-4-yl)methanol (1.00 g, 7.86 mmol) in dichloromethane (20 mL) was slowly added Dess-Martin periodinane (4.17 g, 9.83 mmol) over 10 min at 0 °C. 9.83 mmol) over 10 minutes. The reaction mixture was gradually warmed to room temperature and stirred continuously at this temperature for 60 minutes. After completion of the reaction, the mixture was filtered through diatomaceous earth (Celite) and washed with dichloromethane. The collected organic layer was dried over anhydrous sodium sulfate and subsequently concentrated under reduced pressure. The crude product was purified by column chromatography (eluent: 15% ethyl acetate/hexane) to afford the target product 3,5-dimethyl-4-isoxazolecarboxaldehyde (0.450 g, 46% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 9.92 (s, 1H), 2.68 (s, 3H), 2.31 (s, 3H).
