Lívia Cristina Frota

Iron-Mediated Synthesis of Pyrroles from Cyclopropanes

Significance: The synthesis of highly substituted pyrroles 3 from cyclopropanes 1 and amines 2 via an iron-mediated sequential ring opening–cyclization–dehydrogenation reaction is reported. The conditions were optimized using different solvents, reaction times, and iron catalysts. The scope was studied and cyclopropanes 1 bearing methyl and aryl substituents at R1 were tested with the latter giving better yields. EWGand EDG-substituted aryl amines as well as R2 = OEt were well tolerated. Also, a methyl group in the cyclopropane (R4 = Me) was suitable, furnishing 1,2,3,5-substituted pyrrole 3 in good yield. A series of aromatic and aliphatic amines were screened as well: aliphatic amines furnished pyrroles 3 in low yields, while aromatic amines gave better results, although the yields decrease according to the position of the phenyl substituent. A reaction mechanism involving a radical process was suggested based on radical trapping experiments. Comment: Cyclopropane derivatives can be used as precursors to synthesize a variety of useful heterocyclic motifs (C. A. Carson, M. A. Kerr Chem. Soc. Rev. 2009, 38, 3051; J. R. Green, V. Snieckus Synlett 2014, 25, 2258). The present work reports an efficient synthesis of triand tetrasubstituted pyrroles in moderate to good yields from readily available cyclopropanes and amines. The reaction shows a broad substrate scope; both EWG and EDG in 1 and 2 affording pyrroles 3 in comparable yields. While anilines with different patterns of substitution furnished 3 in good yields, a large excess of amine was required when benzylamines were used. The readily available cyclopropanes can be easily prepared in high yields by the reaction of a dicarbonyl compound with 1,2dibromoethane (Z. Zhang et al. Angew. Chem. Int. Ed. 2007, 46, 1726). R1 O

Manganese-Mediated Coupling Approach to Fused Lactone-Pyrrolidinones

1017 A . W. J . L O G A N , S . J . S PR A G UE , R . W . FO S T E R , L . B . M A R X, V . G A R Z Y A, M . S . H A L L S I D E , A . L . T H O M P S O N, J . W . BU R T O N * ( U NI VE RS I T Y O F O X F O R D A N D G L A X O SM I T H KL I NE , H A R L O W, UK ) Diastereoselective Synthesis of Fused Lactone-Pyrrolidinones; Application to a Formal Synthesis of (–)-Salinosporamide A Org. Lett. 2014, 16, 4078–4081.