铜铁共催化实现尿素作为氰源的碘代芳烃的氰化

Cu/Fe-catalyzed cyanation of aryl iodides using urea

尿素作为一种大宗氮肥,将其作为廉价、易得的化工原料用于高附加值产品的生产已经引起了广泛关注.然而,由于尿素具有较高的热力学稳定性,以其为原料经C–N或C–O键重构的选择性催化转化极具挑战.本文实现了以尿素作为"CN"源的碘代芳烃氰基化反应.该体系无需使用配体,以催化量的CuO和Fe(Ⅱ)盐作为共催化剂,硅烷为还原剂,对于多种碘代芳烃类底物均能以中等到优秀的产率得到相应的腈类产物(包括^(13)C/^(15)N标记的芳腈).本文对反应机理进行了初步探索,反应历程为硅基异氰酸酯中间体对铜(Ⅲ)-碳键的插入和随后的1,3-硅基迁移.

The fertilizer urea can be treated as a cheap and available raw material for chemical production. However,due to the high thermos-stability, its catalytic utilization involving C–N or C–O bond cleavage is highly challenging. The catalytic transformation of its C–N moiety into a nitrile group is attractive, albeit unknown for organic synthesis. Herein,a ligand-free copper-catalyzed cyanation of aryl iodides using urea is described for the first time, which has the potential to be applied as an alternative practical cyanation method. Being co-promoted by catalytic amounts of CuO and Fe(Ⅱ)salts, various aryl iodides were transformed smoothly and the corresponding aryl nitriles including 13C/15N-labeled ones were obtained in moderate to excellent yields. Mechanistic studies support the formation of silyl isocyanates inserting into a copper-carbon bond and the subsequent 1,3-silyl N-to-O migration as the crucial driving force to form C–N triple bonds.