Metal-Free Oxidative Cyclization of Urea-Tethered Alkenes with Hypervalent Iodine

A metal-free oxidative cyclization of ureas onto unactivated alkenes using iodosylbenzene and an acid promoter is described. The products isolated are predominantly bicyclic isoureas resulting from an intramolecular oxyamination reaction. The acid type and urea substitution have a strong effect on the product formed. A variety of substrates form the isourea with high diastereoselectivity via syn addition including di- and trisubstituted alkenes. Hydrolysis of the isourea gives access to new diastereomerically pure prolinol derivatives.

本文描述了一种利用碘苯和酸催化剂在不活泼烯烃上对脲进行金属-free氧化环合反应的方法。所得产物主要为通过分子内氧氨化反应生成的双环异脲。酸的类型和脲的取代基对形成的产品有显著影响。多种底物通过与烯烃的加成反应形成异脲，表现出高度的手性选择性，包括二取代和三取代烯烃。异脲的水解可得到新的对映选择性纯丙氨酸衍生物。