Synthesis of unsymmetrical urea from aryl- or pyridyl carboxamides and aminopyridines using PhI(OAc)<sub>2</sub><i>via in situ</i> formation of aryl- or pyridyl isocyanates
作者:Joydev K. Laha、Neha Singh、Mandeep Kaur Hunjan
DOI:10.1039/d1nj03160k
日期:——
previously, attempts have been made to trap the isocyanates. While the three pyridylisocyanates were trapped as their corresponding carbamates, 3-pyridylisocyanate was isolated and characterized. Unlike closely related previous methods reported for urea synthesis, the current method avoids direct use of isocyanates or eliminates the use of toxic phosgene for the in situ generation of isocyanates.
不对称脲的串联合成(ñ -芳基- Ñ '-pyridylurea和Ñ,ñ从芳基-或吡啶基羧酰胺和氨基吡啶'-bipyridylurea)经由已报道霍夫曼重排。具体而言,苯甲酰胺、吡啶甲酰胺、烟酰胺和异烟酰胺在PhI(OAc) 2存在下原位生成反应性中间体异氰酸酯,其在与氨基吡啶进一步反应后形成尿素衍生物。如从它们相应的羧酰胺的形成pyridylisocyanates的经由霍夫曼重排以前仍未被探索,已尝试捕获异氰酸酯。虽然三种吡啶基异氰酸酯被捕获为其相应的氨基甲酸酯,但 3-吡啶基异氰酸酯被分离并表征。与之前报道的尿素合成方法密切相关,目前的方法避免直接使用异氰酸酯或消除使用有毒光气原位生成异氰酸酯。