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. 2009 Jun 27;65(26):5056-5061.
doi: 10.1016/j.tet.2009.02.021.

Regioselective rhodium-catalyzed intermolecular [2+2+2] cycloaddition of alkynes and isocyanates to form pyridones

Kevin M Oberg  1 , Ernest E Lee, Tomislav Rovis
Affiliations

Regioselective rhodium-catalyzed intermolecular [2+2+2] cycloaddition of alkynes and isocyanates to form pyridones

Kevin M Oberg et al. Tetrahedron. .

Abstract

A highly regioselective rhodium-catalyzed intermolecular [2+2+2] cycloaddition of terminal alkynes with a variety of isocyanates to provide 2- and 4-pyridones has been developed. This reaction proceeds in good to excellent yields and overcomes the problem of dimerization and trimerization through the use of phosphoramidite ligands. A CO migration in the metallacycle is proposed to account for the formation of 4-pyridone.

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Figures

Scheme 1
Scheme 1
Precedent for metal-catalyzed [2+2+2] pyridone forming cycloadditions
Scheme 2
Scheme 2
Rhodium-catalyzed [2+2+2] pyridone forming cycloadditions with terminal alkynes
Scheme 3
Scheme 3
Proposed mechanism
See this image and copyright information in PMC

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