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 undergo a formal (4+2) cycloaddition reaction with dihydro-2,3-furandione, providing an unprecedented route 3,6-dihydropyran-2-ones as spiro[4.5]decane derivatives up 98 % ee thanks the commercially available Takemoto catalyst. Preliminary investigation showed that this could extended other activated ketones, establishing these novel C4-synthon in series.