Reaction of Alkynes and Azides: Not Triazoles Through Copper-Acetylides but Oxazoles Through Copper-Nitrene Intermediates
作者:Estela Haldón、Maria Besora、Israel Cano、Xacobe C. Cambeiro、Miquel A. Pericàs、Feliu Maseras、M. Carmen Nicasio、Pedro J. Pérez
DOI:10.1002/chem.201303737
日期:2014.3.17
Well‐defined copper(I) complexes of composition [Tpm*,BrCu(NCMe)]BF4 (Tpm*,Br=tris(3,5‐dimethyl‐4‐bromo‐pyrazolyl)methane) or [Tpa*Cu]PF6 (Tpa*=tris(3,5‐dimethyl‐pyrazolylmethyl)amine) catalyze the formation of 2,5‐disubstituted oxazoles from carbonyl azides and terminal alkynes in a direct manner. This process represents a novel procedure for the synthesis of this valuable heterocycle from readily
[ Tpm * ,Br Cu(NCMe)] BF 4(Tpm * ,Br = tris(3,5-二甲基-4-溴代吡唑基)甲烷)或[Tpa * Cu]的定义明确的铜(I)配合物PF 6(TPa *= tris(3,5-二甲基-吡唑烷基甲基)胺直接催化羰基叠氮化物和末端炔烃形成2,5-二取代的恶唑。该过程代表了一种从容易获得的起始原料合成这种有价值的杂环的新颖方法,仅导致2,5-异构体,证明了其完全的区域选择性转化。通过实验证据和计算研究,提出了基于铜-酰基氮烯物种初始形成的反应机理的建议,与引发铜催化的炔烃和叠氮化物环加成反应(CuAAC)的众所周知的机理相反通过形成铜-乙炔化物络合物。