O1C2C=CC=C[C:4]=2[CH:3]=N1.[OH:10][C:11]1[C:15]2[CH:16]=[CH:17][C:18]([O:20][CH3:21])=[CH:19][C:14]=2[O:13][N:12]=1.C(O)C.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.CC(OC(/N=N/C(OC(C)C)=O)=O)C>C1COCC1>[CH2:3]([O:10][C:11]1[C:15]2[CH:16]=[CH:17][C:18]([O:20][CH3:21])=[CH:19][C:14]=2[O:13][N:12]=1)[CH3:4]
Benzisoxazole from part (b) (193 mg, 1.17 mmol), ethanol (75 μl, 1.29 mmol) and triphenylphosphine (460 mg, 1.75 mmol) were dissolved in anhydrous THF (4 ml) and cooled)(0°). Diisopropylazodicarboxylate (345 μl, 1.75 mmol) was added slowly and after 10-15 min the reaction flask was removed from the ice bath and the reaction mixture was stirred at room temperature overnight under an argon atmosphere. The solution was evaporated to dryness and the residue pre-absorbed onto silica, and chromatographed on silica (19 g); eluent: hexane (300 ml), 10-30% ethyl acetate/hexane to give 3-ethoxy-6-methoxy-1,2-benzisoxazole (101 mg, 44%) as white crystals.
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