The intermolecular hydro-oxycarbonylation of internal alkynes: current state of the art

The intermolecular addition of carboxylic acids to alkynes is one of the most straightforward and atomeconomical methods currently available for the preparation of synthetically useful enol esters. However, the vast majority of works have focused on the use of terminal alkynes, substrates much more reactive than their corresponding internal counterparts. In fact, efficient and general protocols for hydro-oxycarbonylation of internal alkynes have only seen the light in recent years. In the present review article an overview of the progress made in the field is given. Catalytic reactions promoted by ruthenium, palladium, silver and gold complexes/salts, along with some specific metal-free protocols, are covered.