Oxidative heterocoupling of lithium 2-methylpropanoate α-carbanion and secondary α-carbanions of lithium acylates

When the α-carbanion of 2-methylpropanoate (A) reacts with the α-carbanions of lithium butanoate, pentanoate, hexanoate, heptanoate and phenylacetate (B) in the presence of 1,2-dibromoethane, a mixture of oxidative homocoupling (A-A, B-B) products [2,2,3,3-tetramethyl- and 2,3-diethyl- (or 2,3-dipropyl-, 2,3-dibutyl-, 2,3-dipentyl-, 2,3-diphenyl)succinic acids] and heterocouplings (A-B) products [2,2-dimethyl-3-ethyl- (or 2,2-dimethyl-3-propyl-, 2,2-dimethyl-3-butyl-, 2,2-dimethyl-3 -pentyl-, 2,2-dimethyl-3-phenyl)succinic acids] is formed with a total yield of 84–98%. The effect of the nature of the oxidizing reagent (1,2-dibromoethane and other reagents) and the molar ratio of coupling α-carbanions of lithium acylates on the selectivity of the formation of homo- and heterocoupling products was studied.