A new route to substituted furocoumarins via copper-catalyzed cyclization between 4-hydroxycoumarins and ketoximes was developed. CuBr₂ exhibited higher activity than other copper salts, affording the desired furocoumarins in high yields. The transformation proceeded readily in the absence of stoichiometric external oxidants. The significance of this synthetic strategy would be (1) the easily available starting materials; (2) low cost catalyst CuBr₂; and (3) being without stoichiometric external oxidants. This protocol is complementary to previous approaches in the synthesis of substituted furocoumarins.

中文翻译：

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通过4-羟基香豆素和酮肟之间的铜催化环化反应 获得取代的呋喃香豆素的新途径†

开发了一种通过4-羟基香豆素和酮肟之间的铜催化环化反应取代呋喃香豆素的新途径。CuBr ₂表现出比其他铜盐更高的活性，从而以高收率提供了所需的呋喃香豆素。在没有化学计量外部氧化剂的情况下，转化容易进行。这种综合策略的意义将是：（1）容易获得的起始材料；（2）低成本催化剂CuBr ₂；（3）没有化学计量的外部氧化剂。该协议是取代呋喃香豆素合成中先前方法的补充。