General procedure for the synthesis of 3-methyl-3-formyl-1-oxetane from 3-methyl-3-hydroxymethyl oxetane: 3-methyl oxetan-3-ylmethanol (6.0 g, 58.75 mmol) was dissolved in dichloromethane (117 mL). Trichloroisocyanuric acid (13.93 g, 59.92 mmol) followed by 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) (0.92 g, 5.87 mmol) was added in batches at -5°C. The reaction mixture was then dissolved in dichloromethane (117 mL). The reaction mixture was stirred at -5°C for 20 min, then slowly warmed to room temperature and continued stirring for 20 min. Upon completion of the reaction, the mixture was filtered through a pad of diatomaceous earth (CELITE) and diluted with dichloromethane (200 mL). The organic phase was washed sequentially with saturated aqueous sodium carbonate solution (100 mL), 1N hydrochloric acid (100 mL) and brine (50 mL). Concentration of the organic phase afforded 3-methyl-3-formyl-1-oxetane as an orange oil (4.17 g, 71% yield), which could be used for subsequent reactions without further purification. The product was confirmed by NMR hydrogen spectrum (400 MHz, CDCl3): δ 1.48 (s, 3H), 4.50 (d, 2H, J = 6.34 Hz), 4.88 (d, 2H, J = 6.34 Hz), 9.95 (s, 1H).
