Synthesis of quinol-4-ones and chroman-4-ones via a palladium-catalysed cascade carbonylation–allene insertion

Palladium(0)-catalysed termolecular queuing processes involving oxidative addition to aryl iodides followed by low pressure carbonylation, allene insertion and capture of the resulting π-allyl palladium(II) species by an internal O- or N-nucleophile occur in good yields. One-pot 3-methylene chromanone/quinolone synthesis–Michael addition–stereoselective reduction are also reported.