Cycloaddition of Benzyne with Alkoxy Substituted Pyrroline-N-oxides: Unexpected Rearrangement to a N-Phenylpyrrole

Reaction of enantiopure 3,4-dialkoxy-pyrroline N-oxides with benzyne affords the predictable tetrahydrobenzo[d]pyrrolo[1,2-b]isoxazoles along with an unexpected 2,3-disubstitued–N-phenyl-pyrrole derived by a unprecedented rearrangement of the bis-adduct of nitrone with two molecules of benzyne. A mechanism for the unusual rearrangement is proposed. The benzo[d]isoxazolidine derivatives are conveniently converted to 2-(2-hydroxyphenyl)-3,4-dialkoxypyrrolidines by reductive opening of the N-O bond.