Palladium-catalysed inter- and intramolecular formation of C-O bonds from allenes

The Pd-catalysed formation of a C-O bond from allenes mainly occurs via the inter-or intramolecular reaction with a hydroxyl group belonging to an alcohol, a phenol or an acid. A carbonyl or a carbonate entity can also be involved. In most cases, the formation of the C-O bond is one step of a domino reaction leading also to a C-C or C-N bond, or to another C-O bond. Thus, a wide range of products, in particular highly functionalized heterocycles, have been synthesised. Catalytic cycles have been proposed but the mechanisms often remain speculative.