428516-80-7Relevant academic research and scientific papers
4-Substituted 2,3-dihydroisoxazoles as masked azomethine ylides: Access to pyrrole derivatives by 1,5- and 1,7-dipolar electrocyclizations of enynyl derivatives
Friebolin, Wolfgang,Eberbach, Wolfgang
, p. 3822 - 3836 (2007/10/03)
The enynyl-substituted 2,3-dihydroisoxazoles ('isoxazolines') 9-14 were prepared by highly (Z)-selective Peterson olefination reaction from the corresponding carbaldehydes 6-8. On short-time thermolysis (280-406°/10 s) the TMS derivatives 9-11 give rise to the annulated pyrrolines 18-20, which, in some cases, suffer CH4 elimination affording the pyrroles 15-17. In contrast, thermolysis of the terminal alkyne derivatives 12-14 leads to the bicyclic compounds 21-23. The reaction pathways are discussed on the basis of the formation of conjugated azomethine ylides as key intermediates, which either undergo a 1,5-cyclization to 18-20 or a 1,7-ring-closure affording cycloallene intermediates of type V, which are further transformed into the azepino pyrroles 21-23.
