Photochemical assisted novel formation of δ-lactone utilizing trimethylsilylacetylene, isopropanol and ironpentacarbonyl

•Novel method for the formation of (tricarbonyl)iron complex of δ-lactone or 2-pyranone.•Cyclization of acetylene, iso-propanol and CO produces the δ-lactone or 2-pyranone.•Demetalation of (tricarbonyl)iron complex of δ-lactone or 2-pyranone.•Single crystal X-ray diffraction analysis of (tricarbonyl)iron complex of δ-lactone or 2-pyranone.