Asymmetric Rhodium-Catalyzed [4+3] Cycloaddition

doi:10.1055/s-2007-991248

Synfacts 2007(11): 1161-1161
DOI: 10.1055/s-2007-991248

Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions

Asymmetric Rhodium-Catalyzed [4+3] Cycloaddition

Rezensent(en):Mark Lautens, Praew Thansandote

R. P. Reddy, H. M. L. Davies*
The State University of New York, Buffalo, USA
Asymmetric Synthesis of Tropanes by Rhodium-Catalyzed [4+3] Cycloaddition
J. Am. Chem. Soc. 2007, 129: 10312-10313

Abstract

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Key words

rhodium - tropanes - [4+3] cycloaddition

Significance

A novel methodology for the asymmetric synthesis of tropanes (a popular natural product scaffold) is described using a rhodium-catalyzed [4+3] cycloaddition between pyrroles and a vinyldiazoacetate. The reaction tolerates a wide range of substituted pyrroles with good yields and excellent enantioselectivities. The products can be an intermediate or a precursor to an intermediate in several previously reported syntheses of biologically active tropanes.

Comment

The reaction proceeds by a tandem cyclopropanation-Cope rearrangement. The best catalyst for this reaction is Rh₂(S-PTAD)₄, which limits the formation of some commonly observed side products. The reaction temperature is critical to achieve high conversions.

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