Preparation of Substituted 2H-Pyrans via a Cascade Reaction from Methyl Coumalate and Activated Methylene Nucleophiles

What is it about?

The reaction of methyl coumalate with a wide range of methylene active compounds, such as keto-esters or keto-sulfones and cyclic or acyclic diketones, afforded large variety of 2,3,5,6-tetrasubstituted 2H-pyrans. The reaction proceeds via a cascade reaction involving a Michael addition-6π-electrocyclic ring opening-proton transfer and 6π electrocyclization, in which a variety of functional groups were tolerated

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Why is it important?

This is an efficient green alternative to other methods of preparation of 2H-pyrans. The domino process described in this report takes place in EtOH as solvent and K2CO3 as base. These chemicals are environmentally safe.