Stereoselectivity in 1,3-Dipolar Cycloaddition Reactions of 2-Benzopyrylium-4-olate with Acrylic Acid Derivatives Catalyzed by Rare Earth Metal Triflates

Abstract

The addition of Yb(OTf)₃ or Lu(OTf)₃ was found to be quite effective in obtaining exo-selectivity (up to 87:13) in the reaction of 2-benzopyrylium-4-olate, which was generated by the Rh₂(OAc)₄-catalyzed decomposition of o-methoxycarbonyl-α-di­azoacetophenone, with 3-acryloyl-2-oxazolizinone. The stereoselectivity of the rare earth metal triflate-catalyzed reaction was strongly influenced by the ionic radius of the rare earth metal element, a larger or smaller ionic radius than that of Lu³⁺ resulted in decreased exo-selectivity.

Key words

1,3-dipolar cycloaddition - carbonyl ylide - rare earth metal triflate - stereoselectivity

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