Fe(II)/Et3N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

Ekaterina E Galenko; Olesya A Tomashenko; Alexander F Khlebnikov; Mikhail S Novikov; Taras L Panikorovskii

doi:10.3762/bjoc.11.189

Fe(II)/Et3N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

Beilstein J Org Chem. 2015 Sep 24:11:1732-40. doi: 10.3762/bjoc.11.189. eCollection 2015.

Authors

Ekaterina E Galenko¹, Olesya A Tomashenko¹, Alexander F Khlebnikov¹, Mikhail S Novikov¹, Taras L Panikorovskii²

Affiliations

¹ Institute of Chemistry, Saint Petersburg State University, Universitetskii pr. 26, 198504, St. Petersburg, Russia.
² Institute of Earth Sciences, Saint Petersburg State University, University Emb. 7/9, 199034, St. Petersburg, Russia.

Abstract

A simple approach was developed for the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates from easily available compounds, 5-methoxyisoxazoles and phenacylimidazolium salts under hybrid Fe(II)/Et3N relay catalysis. The products were easily transformed into the corresponding 3-(5-methoxycarbonyl-1H-imidazol-3-ium-3-yl)pyrrol-1-ides, which in turn can be hydrolyzed under basic conditions into the corresponding betaines. A carbene tautomeric form of the 4-methoxycarbonyl-substituted imidazolylpyrrolides was trapped by reaction with sulfur affording the corresponding imidazolethiones under very mild conditions.

Keywords: NHC carbene; imidazole; isoxazole; pyrrole-2-carboxylate; relay catalysis.