Catalytic Oxidative Cyclization of 2′-Arylbenzaldehyde Oxime Ethers under Photoinduced Electron Transfer Conditions
作者:Julie L. Hofstra、Brittany R. Grassbaugh、Quan M. Tran、Nicholas R. Armada、H. J. Peter de Lijser
DOI:10.1021/jo502324z
日期:2015.1.2
sequence is initiated by an electron transfer step followed by nucleophilic attack of the aryl ring onto the nitrogen of the oxime ether. A concave downward Hammett plot is presumably the result of a change in charge distribution in the radical cation species with strongly electron-donating substituents that yields a less electrophilic nitrogen atom and a decreased amount of cyclized product. The reaction
合成了一系列2'-芳基苯甲醛肟醚,显示出在9,10-二氰基蒽存在下于乙腈中照射后生成相应的菲啶。机理研究表明,氧化环化反应顺序是由电子转移步骤引发的,随后芳基环发生亲核性攻击,并与肟醚的氮原子发生反应。向下凹的哈米特图可能是具有强给电子取代基的自由基阳离子物种中电荷分布变化的结果,该变化产生了较少的亲电子氮原子并减少了环化产物的量。该反应具有选择性(与涉及醛肟醚的其他光化学反应不同,不会形成腈副产物),并且在使用带有2'-芳基的化合物时具有区域特异性间取代基,使该反应成为制备取代的菲啶的有用替代方法。