In THF at -78°C, organolithium derivatives and unprotected α, β-unsaturated carboxylic acids give a conjugated addition reaction. Reactions of 1- and 2-naphthoic acids with various organolithium derivatives and electrophiles are reported. Two X-ray studies show that the reaction occurs with a good diastereoselectivity: the dilithiated enolate formed as an intermediate adds the electrophile exclusively via the face opposite to that of the organolithium. A study of the 1 H NMR spectra of the products obtained shows that these compounds adopt a preferred conformation in solution. The protonolysis of the intermediate enolate by trifluoroacetic acid in an inverted mode gives rise to the formation of 1,2-disubstituted dihydronaphthalenes. With acyclic α, β-unsaturated carboxylic acids, the diastereoselectivity of the reaction is marginal. With secondary butyllithium, the protonolysis of the intermediate enolates gives a 1,4-addition and an average diastereoselectivity. Reaction of phenylpropiolic acid with butyllithium gives rise to the formation of a product resulting from a trans addition to the triple bond; the organolithium derivative adds in α to the carboxylic group.Key words: 1,4-addition reactions, carboxylic acids, organolithium derivatives.[Journal Translation]
Asymmetric Hetero-Michael Additions to α,β-Unsaturated Carboxylic Acids by Multifunctional Boronic Acid Catalysts