Dioxopyrroline. LIV. Stereochemical Pathway of (2+2)Photocycloaddition Reaction of 4,5-Diethoxycarbonyl-1H-pyrrole-2,3-dione to Acyclic Olefins.
作者:Takehiro SANO、Hiroshi ENOMOTO、Yasuko KUREBAYASHI、Yoshie HORIGUCHI、Yoshisuke TSUDA
DOI:10.1248/cpb.41.471
日期:——
The photocycloaddition reaction of 4, 5-diethoxycarbonyl-1H-pyrrole-2, 3-dione 4 to acyclic olefins proceeded in a regioselective manner to give two head to tail adducts, the exo- (5) and endo-isomers (6). The stereochemistry of the 7-substituents of the adducts changed depeding on the electronic properties of olefins. Olefins with O-substituents(ethoxyethylene, acetoxyethylene) stereoselectively gave the endo-adducs (6d, e). Olefins with phenyl and ethyl substituents, styrene and 1-butene, gave a mexture of the exo- (5a, b) and endo-adducts (6a, b) with exo-preference.Butadiene gave the exo- (5b) and endo-adduct (6b) with slight excess of the latter. These stereochemical results are in good accordance with the predictions obtained by the sterep-selection rule of enone-olefin photocycloaddition.
4, 5-二乙氧基羰基-1H-吡咯-2, 3-二酮 4 与无环烯烃的光环加成反应以区域选择性方式进行,得到两种头尾加合物,即外型异构体 (5) 和内型异构体 (6)。加合物的7位取代基的立体化学根据烯烃的电子性质而变化。具有O-取代基(乙氧基乙烯、乙酰氧基乙烯)的烯烃立体选择性地产生内加合物(6d,e)。具有苯基和乙基取代基的烯烃、苯乙烯和 1-丁烯,产生外型- (5a, b) 和内型加合物 (6a, b) 的混合物,具有外型优先。丁二烯产生外型- (5b) 和内型-加合物(6b),后者稍微过量。这些立体化学结果与烯酮-烯烃光环加成立体选择规则得到的预测非常一致。