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 pi-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. (C) 2000 Elsevier Science Ltd. All rights reserved.