Oxalyl Chloride (5.9 mL) was added at −70° C. to a solution of dimethylsulfoxide (4.98 mL) in dry dichloromethane (60 mL) and the mixture stirred for 1 hour. 8-(tert-Butyldimethylsilyloxy)-2,2-dimethyloctan-1-ol (example 279, step b) (10.11 g), dissolved in dichloromethane (20 mL), was added dropwise and the mixture allowed to stir for 1 hour. Triethylamine (19.4 mL) was then added and stirring continued for 1 hour. The cooling bath was removed and the mixture allowed to warm to room temperature, at which point DCM (15 mL) was added. 1N HCl was added dropwise to dissolve the salts present in the reaction mixture and the layers separated. The aqueous layer was extracted with DCM (2×250 mL) then the combined organic layers were washed with saturated aqueous sodium carbonate (250 mL), dried over magnesium sulfate, filtered and concentrated under vacuum to give an orange liquid. The residue was filtered through a short plug of silica using diethyl ether as the eluent to afford 8-(tert-butyl-dimethyl-silanyloxy)-2,2-dimethyl-octanal as a yellow liquid which was used without further purification.
