[CH:1]([C:3]1[N:8]=[N:7][C:6]2[O:9][CH2:10][CH2:11][CH2:12][C:5]=2[CH:4]=1)=C.O.I([O-])(=O)(=O)=[O:15].[Na+]>O1CCOCC1.[Os](=O)(=O)(=O)=O>[N:7]1[C:6]2[O:9][CH2:10][CH2:11][CH2:12][C:5]=2[CH:4]=[C:3]([CH:1]=[O:15])[N:8]=1
A solution of 3-ethenyl-6,7-dihydro-5H-pyrano[2,3-c]pyridazine (100 mg, 0.617 mmol) in 1,4-dioxane (5.5 ml)/water (1.1 ml) was cooled in ice/water and treated with sodium periodate (306 mg, 1.43 mmol) and a 4% aqueous solution of osmium tetroxide (0.55 ml). The mixture was allowed to warm to rt after an hour, and after a total of 4.75 h stirring, the solvent was evaporated. 1,4-Dioxane was added and evaporated, a few ml of DCM were added and the mixture briefly held in an ultrasonic bath. The whole mixture was applied to a silica column and eluted with ethyl acetate to give the product (55 mg, 54%).
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