4-Nitroisoxazoles as nitroalkene heterodienes: diastereoselective synthesis of spiro tricyclic nitroso acetals by thermal reactions with ethyl vinyl ether

A few 4-nitroisoxazoles were found to undergo highly diastereoselective pericyclic homodomino processes with the title enol ether affording 1,6,9-trioxa-5,9a-diazacyclopenta[d]indenes through bicyclic nitronates as key intermediates. Formation of isoxazolo–oxepine systems is also reported together with a domino reaction with the above reagent and methyl acrylate. Two X-ray analyses of compounds 8 and 13 were carried out to firmly establish their stereochemistry.