(TFE) promoted synthesis of unsymmetric ureas was described. This approach enabled the construction of a variety of ureas from the readily prepared and easy-to-handle dioxazolones and amines viatandem Lossen rearrangement/condensation process. The reaction featured mild conditions for the urea synthesis under metal-free conditions, which was successively applied in the scale-up synthesis of herbicides
Metal-Free Oxidative C-H Amidation of<i>N</i>,<i>N′</i>-Diarylureas with PhI(OAc)<sub>2</sub>: Synthesis of Benzimidazol-2-one Derivatives
作者:Jipan Yu、Chang Gao、Zhixuan Song、Haijun Yang、Hua Fu
DOI:10.1002/ejoc.201500726
日期:2015.9
compounds or intramolecular N-arylations using substrates with carbon-halogen bonds. However, the starting materials of these protocols are often not readily available. Herein, a simple and practical metal-free oxidative C–H amidation of N,N′-diarylureas has been developed that takes place at room temperature. This protocol uses readily available N,N′-diarylureas as the starting materials and inexpensive
alkylation of a methyl group, on di‐ and trisubstituted ureas, with terminalalkenes by C(sp3)−Hbondactivation proceeded in the presence of a hydroxoiridium/bisphosphine catalyst to give high yields of the corresponding addition products. The hydroxoiridium/bisphosphine complex generates an amidoiridium intermediate by reaction with ureas having an N−H bond.
benzimidazol-2-one synthesis under transition-metal-free conditions. The required 1,3-diarylurea substrates are readily accessible by the addition of N-substituted arylamines to the corresponding isocyanates. This versatile and operationally simple synthetic process is broadly applicable to a wide range of 1,3-diarylureas and provides facile access to benzimidazol-2-ones and relatedheterocycles. Moreover,
Unsymmetrical N,N'-diarylureas may be alkylated regioselectively at the more sterically congested nitrogen atom. The resulting mono-N-alkylated ureas undergo directed metalation (ortholithiation) with sec-BuLi to yield, on electrophilic quench, products functionalized regioselectively at the ring bearing the alkylated nitrogen atom.