Formation of Cyclic ‘<i>ortho</i>’-Anhydrides of Heptalene-1,2-dicarboxylic Acids
作者:Roland H. Weber、Paul Brügger、Wolf Arnold、Peter Schönholzer、Hans-Jürgen Hansen
DOI:10.1002/hlca.19870700602
日期:1987.9.23
oxylic acids as well as 2-(alkoxycarbonyl)heptalene-1-carboxylic acids react with the iminium salt formed from N,N-dimethylformamide (DMF) and oxalyl chloride, in the presence of an alcohol, to yield the corresponding cyclic ‘ortho’ -anhydrides (ψ-esters; cf. Schemes 2,3,6, and 8). When the alkoxy moiety of the acids and the alcohols is different, then diastereoisomeric ‘ortho’ -anhydrides are formed
1-(烷氧羰基)庚二烯-2-羧酸以及2-(烷氧基羰基)庚二烯-1-羧酸在醇存在下与由N,N-二甲基甲酰胺(DMF)和草酰氯形成的亚胺盐反应,得到相应的环状“邻”-酸酐(ψ-酯;参见方案2、3、6和8)。当酸和醇的烷氧基部分不同时,由于庚烯骨架的非平面性,形成非对映异构的“邻”-酸酐。强烈建议从β侧使用醇(参见方案5和表1))。该效应可以归因于庚烯骨架的弯曲拓扑,其在空间上阻碍亲核试剂从假定的中间体,即19型带电荷的O-烷基化的酸酐的α-侧接近(参见方案6)。而“邻位‘-anhydrides与在‘围’的庚搭烯骨架的位上四个取代基是结构稳定达100°时,’邻位” -anhydrides只有三个“围” -取代基差向异构化缓慢,在100℃(CF方案7)归因于庚烯骨架的构型的热诱导反转。