Ring transformations of 2,3-dihydroisoxazoles via azomethine ylides -formation of annulated 5-and 7-membered N-heterocycles

摘要

On thermal activation teh 2,3-dihydroisoxazoles 12-14 are transformed into annulated dihydroazepines 15-17 as main products, besides minor amounts of the corresponding pyrrole derivatives 18-20. In the proposed mechanism the azomethine ylides of type III and VI are involved as intermediates which undergo 1,5- and 1,7-ring closure reactions,respectively.