1. 20.5 mL (0.25 mol) of cis-1,2-dihydroxymethylene and 105 mL (0.75 mol) of triethylamine were dissolved in 400 mL of tetrahydrofuran at room temperature, and 60 mL (0.63 mol) of acetic anhydride was added slowly with stirring. The reaction mixture was stirred for 16 hours and then the reaction was terminated by adding 300 mL of saturated aqueous sodium chloride solution. Subsequently, sodium bicarbonate solution and 300 mL of diethyl ether were added for extraction. The aqueous phase was further extracted with 200 mL of diethyl ether and the organic phases were combined, washed with 300 mL of saturated saline, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by reduced pressure distillation (3 mbar, 80-82°C) to give 39.3 g cis-1,4-diacetoxy-2-butene in 91% yield (based on cis-1,2-dihydroxymethylene).
2. 17.2 g of cis-1,4-diacetoxy-2-butene (100 mmol) was dissolved in a solvent mixture of 150 mL of acetone and 50 mL of water, to which were added 26 g of N-methylmorpholine-N-oxide (NMO, 200 mmol) and 270 mg of osmium tetroxide (OsO4-H2O, 0.75 mmol), and the reaction was stirred for 3 hours at room temperature. After TLC monitoring showed that the reaction was complete, the reaction was terminated by adding 300 mL of saturated aqueous sodium bisulfite and 300 mL of ethyl acetate. The aqueous phase was extracted with 600 mL of ethyl acetate, and the organic phases were combined, washed with 400 mL of saturated saline, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to give 18.5 g of diol as white crystals in 90% yield (based on cis-1,4-diacetoxy-2-butene).
3. 8.2 g of the diol (40 mmol) was dissolved in 150 mL of dichloromethane, 80 g of sodium periodate (NaIO4, 55 mmol) was added, and the reaction was stirred at room temperature for 1.4 h. After the reaction was complete as indicated by TLC, the silica was removed by filtration and the filter cake was washed with 100 mL of dichloromethane. The filtrates were combined, concentrated under reduced pressure and the residue was purified by fine distillation to give 4.1 g of the target aldehyde in 50% yield (based on diol). The structure of the product was confirmed by 1H NMR and 13C NMR spectroscopy.
