Rearrangement of isoxazoline-5-spiro derivatives. Part 3. Indolizine, quinolizine and pyrido[1,2-a]azepine derivatives by sequential rearrangement-annulation

Abstract

4,5-Dihydrospiro[isoxazole-5-cyclopropane] derivatives (3), having a functionalized side-chain in position 3, have been prepared by cycloaddition. Under thermolytic conditions, compounds (3), undergo rearrangement to the intermediate 5,6-dihydro-4-pyridones (4) followed immediately by a further cyclization to N-bridgehead bicyclic compounds. A side-product, ascribed a wrong structure in a preliminary communication, is proved by crystallographic analysis to be 2,3,4,4a,5,6-hexahydroquinolin-7(1H)-one (7).