Nitrone Formation by Reaction of an Enolate with a Nitro Group

Ketones with a 2-nitrophenyl group at the alpha-position were treated with sodium hydroxide in methanol at 60 degrees C. Under these conditions, enolates derived from the ketones intramolecularly reacted with the nitro group to form a variety of nitrones. Additional experimental results, including the unexpected isolation of N-hydroxyindolinone as a byproduct, led to a proposed reaction mechanism, occurring via an alpha-hydroxyketone. The resultant nitrones underwent inter- and intramolecular 1,3-dipolar cycloaddition with olefins to afford polycyclic isoxazolidines.

Automated summary

Treatment of ketones with a 2-nitrophenyl group at the alpha-position with sodium hydroxide in methanol at 60 degrees C leads to the formation of various nitrones. Unexpected isolation of N-hydroxyindolinone as a byproduct and proposed reaction mechanism involving an alpha-hydroxyketone. The resulting nitrones undergo inter- and intramolecular 1,3-dipolar cycloaddition with olefins to yield polycyclic isoxazolidines.