Dioxopyrrolines. XLVIII. Regioselective formation of hydroindoles via photochemical and thermal cycloaddition reactions of 5-aryl-4-ethoxycarbonyl-1H-pyrrole-2,3-dione with isoprene.
作者:Takehiro SANO、Yoshie HORIGUCHI、Suetaka KAMBE、Yoshisuke TSUDA
DOI:10.1248/cpb.38.2157
日期:——
Photocycloaddition of 5-aryl-4-ethoxycarbonyl-1H-pyrrole-2, 3-dione 1 with isoprene and thermolysis of the resulting exo-vinyl cyclobutanes 6 caused a ring enlargement reaction due to a 1, 3-shift, giving rise to the hydroindoles 9, which were found to be regioisomeric to the hydroindoles 14 obtained as a major cycloadduct by the Diels-Alder reaction of the same addends. Thus, the two-step hydroindole synthesis, i.e., dioxopyrroline-diene photoannulation and thermolysis of the resulting vinyl cyclobutane, has a synthetic value in giving the product with the reverse regiochemistry to that of the Diels-Alder adduct.
5-芳基-4-乙氧羰基-1H-吡咯-2,3-二酮1与异戊二烯的光环加成及所形成的外向-乙烯基环丁烷6的热解,由于1,3-迁移导致了环扩张反应,产生了羟吲哚9,这些羟吲哚被发现与通过相同加成物的狄尔斯-阿尔德反应主要得到的环加成物14是区域异构体。因此,两步法制备羟吲哚,即二氧吡咯啉-二烯的光环加成和随后乙烯基环丁烷的热解,在获得与狄尔斯-阿尔德加成物相反的区域化学产物的合成价值。