Aryl-substituted dimethylbenzimidazolines as effective reductants of photoinduced electron transfer reactions
作者:Eietsu Hasegawa、Taku Ohta、Shiori Tsuji、Kazuma Mori、Ken Uchida、Tomoaki Miura、Tadaaki Ikoma、Eiji Tayama、Hajime Iwamoto、Shin-ya Takizawa、Shigeru Murata
DOI:10.1016/j.tet.2015.06.071
日期:2015.8
Photoinduced electron transfer (PET) reactions promoted by 2-aryl substituted 1,3-dimethylbenzimidazolines (Ar-DMBIH) were investigated. Excited states of Ar-DMBIH, formed by irradiation using light above 360 nm, initiate PET reductions of various organic substrates, including transformations of epoxy ketones to aldols, free radical rearrangements such as the Dowd-Beckwith ring-expansion and 5-exo
研究了由2-芳基取代的1,3-二甲基苯并咪唑啉(Ar-DMBIH)促进的光诱导电子转移(PET)反应。通过使用360 nm以上的光进行辐照而形成的Ar-DMBIH激发态,可引发PET还原各种有机底物,包括将环氧酮转变为羟醛,自由基重排(如Dowd-Beckwith环扩环和5-外己烯基环化) ,对N脱保护-磺酰基吲哚和酰基甲酸酯的烯丙基化。在这些方法中,具有1-萘基,2-萘基,1-吡啶基和9-蒽取代基的Ar-DMBIH在形式上起两个电子和一个质子供体的作用,而被羟基萘基取代的衍生物充当两个电子和两个质子的供体。根据吸收光谱研究,循环伏安法和DFT计算的结果,提出了这些还原反应的机理顺序,包括对Ar-DMBIH的芳基发色团进行初始光激发,然后单电子转移(SET)到有机物底物产生苯并咪唑啉的自由基阳离子和底物的自由基阴离子。