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Synfacts 2009(11): 1202-1202  
DOI: 10.1055/s-0029-1218136
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Rh-Catalyzed Cycloadditions of Unsymmetrical Alkynes with Isocyanates

Contributor(s): Victor Snieckus, Timothy Hurst
R. Keller Friedman, T. Rovis*
Colorado State University, Fort Collins, USA
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Publication History

Publication Date:
22 October 2009 (online)

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Significance

A Rh-catalyzed regioselective [2+2+2] cycloaddition between unsymmetrical alkynes 1, 5, and 8 and alkenyl isocyanates 2 is presented. The high regioselectivity is controlled by a combination of steric and electronic effects. Substituted alkenes (R² ¹ H) tend to give higher enantioselectivities. A switch in regioselectivity was observed when changing from an EWG to an EDG on the alkyne, which is rationalized on the ability of the alkyne to stabilize adjacent positive charge.