Process for producing delta-lactones

A process for preparing a delta-lactone comprising the steps of

• a) reacting an aldehyde with an unsaturated organic halide in a carbon chain extension reaction, wherein the carbon chain extension reaction is carried out in the presence of water, using a catalyst comprising a mixture of aluminum, copper, tin(II) chloride and sodium iodide or a catalyst comprising a mixture of copper and tin(II) chloride, to form an alcohol compound comprising a functional group capable of allowing for carbonylation of said alcohol compound;
• b) reacting said alcohol compound with a source of carbon monoxide in a carbonylation reaction in the presence of water, using a catalytic system comprising a transition metal and/or a salt of a transition metal wherein the transition metal is selected from cobalt, iridium, palladium, platinum, rhodium, and mixtures thereof, wherein the catalytic system further comprises a tin(II) chloride co-catalyst and a ligand comprising at least one donor atom selected from nitrogen, phosphorous, arsenic, antimony and bismuth to form an hydroxycarboxylic acid;
• and
• c) cyclising the hydroxycarboxylic acid to produce the delta-lactone.