We have investigated the cobalt mediated PausonKhand (PK) reaction in water. In the presence of detergents and surfactants, Co2(CO)8 and Co4(CO)12 are effective under aqueous-phase, thermal PK reactions. In a waterTriton®X-100 medium, Co4(CO)12 is catalytically active. Further, dicobalthexacarbonyl complexes of alkynes and enynes undergo effective cyclization under thermal (70 °C) and NMO-promoted conditions. The oxidative nature of the latter conditions inhibits the reductive PK reaction. In all protocols, moderate to excellent yields of the cycloadducts are obtained. Substrates that are prone to hydrolysis, such as acetals, highly activated carboxylic acid derivatives, and those bearing propargylic heteroatom groups are tolerated under appropriate conditions. Finally, the more challenging intermolecular cycloadditions can also be easily achieved under aqueous conditions.Key words: alkyne, cycloaddition, green chemistry, PausonKhand reaction, water.
我们已经在
水中研究了
钴介导的Pauson-Khand(PK)反应。在存在洗涤剂和表面活性剂的情况下,Co₂(CO)₈和Co₄(CO)₁₂在
水相、热力PK反应中是有效的。在
水-Triton® X-100介质中,Co₄(CO)₁₂具有催化活性。此外,
炔烃和烯
炔烃的二
钴六羰基络合物在热(70°C)和NMO促进条件下进行有效的环化反应。后一条件的氧化性质抑制了还原性PK反应。在所有方案中,环加成产物的产率从中等到优良。易
水解的底物,如
缩醛、高度活化的
羧酸衍
生物以及带有
丙炔基杂原子基团的底物在适当条件下是可容忍的。最后,更具挑战性的分子间环加成也可以在
水相条件下轻松实现。关键词:
炔烃,环加成,绿色
化学,Pauson-Khand反应,
水。