Generation of highly strained 2,3-bridged 2H-azirines via cycloaddition reactions of 2-azidobuta-1,3-dienes and photolysis of the resulting cyclic vinyl azides
作者:Klaus Banert、Andreas Ihle、Andrea Kuhtz、Enrico Penk、Biswajit Saha、Ernst-Ulrich Würthwein
DOI:10.1016/j.tet.2012.12.054
日期:2013.3
and with electron-poor dienophiles to generate the Diels–Alder products 12a,b, 13a,b, 14a,b, 15a,b, and 16b. Both types of reactions provide an access to cyclic vinyl azides, which lead to short-lived 2,3-bridged 2H-azirines 18a,b and 20a,b on photolysis. Whereas the highly strained heterocycle 18b could be characterized by low temperature NMR spectra, the bridgehead azirines 18a and 20a,b were trapped
用二氧化硫处理2-azidobuta-1,3-dienes 10a,b,制备3-azido-3-sulfolenes 11a,b,并用贫电子的亲二烯体生成Diels–Alder产品12a,b,13a,b,14a,b,15a,b和16b。两种类型的反应都提供了进入环状乙烯基叠氮化物的途径,这导致了短寿命的2,3-桥连2 H-叠氮基18a,b和20a,b光解。高应变的杂环18b可以通过低温NMR光谱表征,而桥头基叠氮基18a和20a,b被环戊二烯通过立体选择性[4 + 2]-环加成法或氰化氢捕获而得到双环2-氰基氮丙啶。后者的转化导致化合物22b显示出温度依赖性的1 H NMR光谱,这是因为氮丙啶N原子上的构型快速平衡。然而,高水平的量子化学研究表明,不仅22b的两种反相异构体(内,外),但每个都涉及两个符合标准的人(椅子,船)。