[O:1]1[C:6]2[CH:7]=[CH:8][C:9](C=O)=[CH:10][C:5]=2[O:4][CH2:3][CH2:2]1.C1C=C(Cl)C=C(C(OO)=[O:21])C=1.C([O-])(O)=O.[Na+]>C(Cl)Cl>[O:1]1[C:6]2[CH:7]=[CH:8][C:9]([OH:21])=[CH:10][C:5]=2[O:4][CH2:3][CH2:2]1To a solution of 2,3-dihydro-benzo[1,4]dioxin-6-carboxaldehyde (30.0 g, 183 mmol) in 500 ml CH2Cl2 was added mCPBA (37.85 g, 219 mmol). The suspension was heated to 50° C. After 16 h saturated NaHCO3 was added and the mixture was extracted with CH2Cl2 The combined organics were concentrated in vacuo and taken up in MeOH and 200 ml 4M NaOH was added. After 2 h the mixture was acidified with 4M HCl and extracted with ethyl acetate. The combined organics were washed with saturated NaHCO3, washed with brine, concentrated in vacuo, and taken up in CH2Cl2. The solution was filtered to remove the precipitate. The resulting solution was stirred with saturated NaHCO3 for 1 h, separated, dried over MgSO4, filtered and concentrated in vacuo to give 2,3-dihydro-benzo[1,4]dioxin-6-ol (26.92 g, 94%).
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