A general route to alpha-pyrones and 3-substituted isocoumarins from (Z)-iodovinylic acids 1a-f or 2-iodobenzoic acids 4a-c is described, including compounds bearing a substituent on the aromatic ring. Treatment of (Z)-beta-iodovinylic acids 1a-f or 2-iodobenzoic acids 4a-c with various allenyltributyltin reagents in the presence of palladium acetate, triphenylphosphine, and tetrabutylammonium bromide in dimethylformamide provided good yields of the corresponding alpha-pyrones 3a-k or 3-substituted isocoumarins 5a-g via tandem Stille reaction and 6-endo-dig oxacyclization.

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An easy and mild copper(I)‐catalysed lactonisation of readily available (E)‐2,3‐dihalopropenoic acid derivatives regio‐ and stereoselectively leads to rarely described (Z)‐3‐halo‐5‐ylidene‐5H‐furan‐2‐ones. These compounds are subsequently able to undergo classical Pd‐catalysed cross‐coupling reactions, providing 3‐substituted and 3,4‐disubstituted 5‐ylidene‐5H‐furan‐2‐ones (see scheme).

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