Ethyl 2-cyano-2-(4-nitrophenylsulfonyloxyimino)acetate (4-NBsOXY) mediated Lossen rearrangement and its application for the synthesis of ureas is demonstrated. Required hydroxamic acids for the Lossen rearrangements were synthesized from carboxylic acids using the same reagent. Finally, reaction of an amine with the produced isocyanate resulted in urea. Good yields without racemization were achieved under milder and simpler reaction conditions. Reactions are compatible with common N-protecting groups, such as Boc, Fmoc, Cbz, and benzyl, as well as various OH protecting groups, such as ^tBu and Bzl. Conversion from carboxylic acid to urea is achieved in one pot. Most importantly, byproducts Oxyma [ethyl 2-cyano-2-(hydroxyimino)acetate] and 4-nitrobenzenesulfonic acid can be recovered easily and can be recycled to prepare the reagent. Thus, the method is environmentally friendly and cost-effective.

中文翻译：

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2-氰基-2-（4-硝基苯基磺酰氧基亚氨基）乙酸乙酯介导的丢失重排：从羧酸中单次无外消旋地合成羟肟酸和尿素

证明了2-氰基-2-（4-硝基苯基磺酰氧基亚氨基）乙酸乙酯（4-NBsOXY）介导的洛森重排及其在合成脲中的应用。使用相同的试剂，由羧酸合成用于Lossen重排的所需异羟肟酸。最后，胺与产生的异氰酸酯反应生成尿素。在温和且较简单的反应条件下，无需消旋即可获得良好收率。反应与常见的N保护基团（例如Boc，Fmoc，Cbz和苄基）以及各种OH保护基团（例如^tBu和Bzl。一锅即可完成从羧酸到尿素的转化。最重要的是，副产物Oxyma [2-氰基-2-（羟基亚氨基）乙酸乙酯]和4-硝基苯磺酸可以很容易地回收并可以循环使用以制备试剂。因此，该方法是环境友好的和成本有效的。