Palladium(II)-catalyzed oxidative cyclization of methyl 2-allyl-4,5,6-tribromo-3-hydroxybenzoate 4 gave a mixture of methyl 5,6,7-tribromo-2-methyl-benzofuran-4-carboxylate 5 and methyl 6,7,8-tribromo-2H-1-benzopyran-5-carboxylate 6; the ratio of the two products varied between 71:29 and 24:76 depending on the reaction conditions. On the other hand, NBS or NIS mediated cyclization of 4 followed by treatment with NaOMe or DBU furnished benzofuran derivative 5 in good overall yield.

中文翻译：

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由2-烯丙基-4,5,6-三溴-3-羟基苯甲酸甲酯合成三溴苯并呋喃和三溴苯并吡喃衍生物

钯（II）催化的2-烯丙基-4,5,6-三溴-3-羟基苯甲酸甲酯4的氧化环化反应得到5,6,7-三溴-2-甲基-苯并呋喃-4-羧酸甲酯5和6,7,8-三溴-2 H -1-苯并吡喃-5-羧酸甲酯6 ; 取决于反应条件，两种产物的比例在71:29至24:76之间变化。另一方面，NBS或NIS介导的4的环化，然后用NaOMe或DBU处理提供了良好的总收率的苯并呋喃衍生物5。