Alkylidene Meldrum's Acids as Platforms for the Vinylogous Synthesis of Dihydropyranones

Upon Brønsted base organocatalysis, ketone‐derived alkylidene Meldrum's acids proved to be competent vinylogous platforms able to undergo a formal (4+2) cycloaddition reaction with dihydro‐2,3‐furandione, providing an unprecedented route to 3,6‐dihydropyran‐2‐ones as spiro[4.5]decane derivatives with up to 98 % ee thanks to the commercially available Takemoto catalyst. Preliminary investigation showed that this reaction could be extended to other activated ketones, establishing these alkylidene Meldrum's acids as a novel C4‐synthon in the vinylogous series. Disubstituted alkylidene Meldrum's acids proved to be novel C4‐synthons capable of undergoing a vinylogous formal (4+2) cycloaddition reaction with reactive ketones, providing an unprecedented route to chiral 3,6‐dihydropyran‐2‐ones under Brønsted base organocatalytic conditions.