A STUDY OF THE REACTIVITY OF TRICARBONYL(VINYLKETENE)IRON(0) COMPLEXES TOWARDS ALKYNES

Alkynes add to tricarbony](vinytketene)iron(0) complexes to generate stable 1:1 adducts, the structures of which were determined by an X-ray crystal structure analysis of the adduct formed from tricarbonyl(5-phenyl-3-iso-propyl-1-oxapenta-1,2,4-triene)iron(0) and dimethyl acetylenedicarboxylate. Addition of unsymmetrical alkynes is regioselective and the regiochemistries of the adducts isolated from these reactions were determined by X-my crystal structure analyses of the products derived from but-3-yn-2-one and tricarbonyl(3-tert-butyl-5-phenyl-1-oxapenta-1,2,4-triene)iron(0), and of the structurally modified product derived from diethylpropynylamine and tricarbonyl(5-phenyl-3-iso-propyl-1-oxapenta-1,2,4-triene)iron(0). Thermolysis of the adducts leads to either cyclopentenediones or phenols and its outcome is dependent on the electronic properties of the carbon-1 substituent of the adduct. The phenols may be synthesised directly and regioselectively from tricarbonyl(vinylketene)iron(0) complexes and the appropriate alkynes.