[N:1]1[O:2][N:3]=[C:4]2[C:9](Br)=[CH:8][CH:7]=[CH:6][C:5]=12.C([O:13][B:14](OCC)[O:15]CC)C.[Li]CCCC.[Cl-].[NH4+]>O1CCCC1.CCCCC>[N:1]1[O:2][N:3]=[C:4]2[C:9]([B:14]([OH:15])[OH:13])=[CH:8][CH:7]=[CH:6][C:5]=12To a solution of 4-benzo[c]furazanyl bromide (4 g, 0.020 mol) in tetrahydrofurane (80 ml) and n-pentane (20 ml) is added triethylborate (3.8 ml, 0.022 mol) and N,N,N,N-tetraethylendiamine (3 ml, 0.02 mol). Then, n-BuLi (8.8 ml, 2.5N in hexane, 0.022 mol) is added dropwise at -100° C. and the solution is stirred for 5 minutes more. The reaction mixture is poured into an aqueous solution of saturated ammonium chloride and the water phase is extracted with ethyl acetate. The organic solvent is removed and the crude product is taken up in dichloromethan/n-hexane (5:6). The suspension is filtered to yield the title compound (1.05 g) which is used without further purification.
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