Reaction of [E,E]-hexa-2,4-dienal with nitrosobenzene led regiospecifically to the Diels-Alder cycloadduct which is unstable at room temperature. Its enol form underwent a hetero-Cope rearrangement, giving ultimately the pyrroloindole . Simultaneously base-catalyzed deprotonation of gave the dicarbonyl intermediate which ring-closes in two ways, leading eventually to the betaïne and to small amounts
[E,E] -hexa-2,4-dienal与
亚硝基苯的反应区域特异性地导致Diels-Alder环加合物在室温下不稳定。其烯醇形式经历了异Cope重排,最终得到
吡咯并
吲哚。同时进行碱催化的的去质子化反应,生成以两种方式闭环的二羰基中间体,最终导致
甜菜碱和少量
吡咯。