A Cobalt-Catalyzed Multicomponent Approach to Novel 2,3-Di- and 2,2,3-Trisubstituted 3-Methoxycarbonyl-gamma-butyrolactones

A one-pot, three-component synthesis of the title butyrolactones starting from aryl bromides, dimethyl itaconate, and either aldehydes or ketones is described. The cobalt-catalyzed domino process formally involves the in situ metalation of an aromatic bromide, conjugate addition onto dimethyl itaconate, an aldolization reaction with a carbonyl compound and a final cyclization into a five-membered lactone. This procedure is applied to the concise synthesis of a range of functionalized gamma-butyrolactones with a methyl paraconate subunit.