Multicomponent synthesis of polysubstituted γ-butyrolactones under Barbier-like conditions
The one-pot, three-component synthesis of 2,3-di- and 2,2,3-trisubstituted-3-methoxycarbonyl-γ-butyrolactones starting from aryl bromides, dimethyl itaconate, and aldehydes or ketones is described. The cobalt-catalyzed domino process formally involves the in situ metallation of an aromatic bromide, a conjugate addition onto dimethyl itaconate, an aldolization reaction with a carbonyl compound, and a final cyclization into a five-membered ring lactone. This procedure is applied to the concise synthesis of a range of polyfunctionalized γ-butyrolactones displaying a paraconic acid methyl ester subunit.