A novel organocatalytic approach to γ,γ-disubstituted butenolides is described. It is based on a fully site-selective functionalization of 5-alkylidenefuran-2(5H)-ones via trienamine-mediated [4+2]-cycloaddition with α,β,γ,δ-diunsaturated aldehydes. The developed methodology proceeds with excellent stereocontrol and constitutes a unique example of trienamine chemistry with vinylogous dienophiles. Importantly, the reaction has very broad scope and allows for the introduction of substituents also in the α- or the β-position of the butenolide ring. Usefulness of the products obtained has been confirmed in the intramolecular Stetter reaction leading to polycyclic product.
Keywords: aminocatalysis; asymmetric catalysis; butenolides; cycloaddition; organocatalysis; trienamines.
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