Formation of 2,2-dimethylchroman-4-ones during the photoinduced rearrangement of some aryl 3-methyl-2-butenoate esters. A mechanistic insight
作者:Daniela Iguchi、Rosa Erra-Balsells、Sergio M. Bonesi
DOI:10.1016/j.tet.2016.02.039
日期:2016.4
Several aryl 3-methyl-2-butenoate esters upon irradiation lead to the formation of [1,3]-migrated photoproducts, phenol and, surprisingly 2,2-dimethylchroman-4-one derivatives. The starting photochemical reaction takes place from the singlet excited state of the ester and as a total mechanism two consecutive reaction pathways are proposed. The former involves the photo-Fries rearrangement of the esters
辐照后的几种芳基3-甲基-2-丁烯酸酯会导致[1,3]迁移的光产物,苯酚以及令人惊讶的2,2-二甲基苯并吡喃-4-酮衍生物的形成。起始光化学反应从酯的单重激发态发生,并且作为总机理,提出了两个连续的反应途径。前者涉及酯在所有研究的溶剂中的光-弗里斯重排,并且取决于溶剂的质子性,后者涉及ESIPT过程,然后进行热6π-电环反应和/或热(分子内氧杂-迈克尔加成反应)邻位区域异构体的环化形成。该第二途径负责2,2-二甲基苯并吡喃-4-酮衍生物的形成。