Crown ether 3, containing a pyrrole subcyclic unit, is prepared according to two different synthetic routes. According of the first route 2, 5-bis[3-methyl-2-hydroxyphenyl]pyrrole (2) is cyclized with 1, 11-dibromo-3,6,9-trioxaundecane. According to the second route, a crown ether containing a 1,4-diketone unit is prepared first, followed by cyclization to form the pyrrole subcyclic unit. However, if the cavity in the crown ether ring system is small, the cyclization of 1,4-diketone unit does not success.
含有
吡咯亚环单元的
冠醚 3 是按照两种不同的合成路线制备的。根据第一种路线,2, 5-双[3-甲基-2-羟基苯基]
吡咯(2)与 1, 11-二
溴-3,6,9-三氧杂
十一烷发生环化反应。根据第二条路线,首先制备含有 1,4-二酮单元的
冠醚,然后环化形成
吡咯亚环单元。不过,如果
冠醚环系统中的空腔较小,1,4-二酮单元的环化就不会成功。