[Li+].[OH-].[CH3:3][C:4]1[C:9]2[O:10][CH2:11][CH2:12][O:13][C:8]=2[CH:7]=[C:6]([C:14]([O:16]C)=[O:15])[CH:5]=1.[OH-].[Na+]>O.C1COCC1>[CH3:3][C:4]1[C:9]2[O:10][CH2:11][CH2:12][O:13][C:8]=2[CH:7]=[C:6]([C:14]([OH:16])=[O:15])[CH:5]=1A solution of 6.65 g (0.28 mol) LiOH in 100 mL water was metered into a solution of 33.60 g (0.16 mol) methyl 8-methyl-2,3-dihydro-1,4-benzodioxin-6-carboxylate in 200 mL THF and the reaction solution was stirred overnight at RT. To complete the reaction 150 mL 6 M NaOH were added and the mixture was stirred for a further 2 h at 50° C. The reaction mixture was evaporated down i.vac, the residue was combined with THF, acidified with conc. HCl while cooling with ice, the precipitate was filtered off, washed with 150 mL water and dried at 60° C. in the circulating air dryer.
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