1-Aryl-5-methoxy-pyrrolones as Synthons for 1,3-Dipolar Cycloadditions

A general method is described to convert the title compound into more complex nitrogen heterocyclic systems in a short and attractive pathway. Spiroisoxazolidine 6 was obtained from the reaction of nitrone 3 with ethyl vinyl ether. Chloroformylation of pyrrolone 2 gave 1-aryl-2-chloro-5-methoxy-pyrrol-3-carbaldehyde 4. Substitution of chlorine atom with unsaturated nucleophiles 8a,b and then modifying the aldehyde function into 1,3-dipoles 10 and 14 furnished tricyclic heterocycles 11, 12 and 15 via intramolecular 1,3-dipolar cycloaddition reaction.