Copper(I) or (II)-mediated conjugate addition or dimerisation of functionalised organolithium compounds

The reaction of different functionalised organolithium intermediates 1–3 with several electrophilic olefins 6 (2-cyclopentenone, 2-cyclohexenone, methyl vinyl ketone, benzylideneacetone, benzylideneacetophenone and ethyl acrylate) in the presence of copper(I) salts (bromide and iodide) in THF at −78°C gives, after hydrolysis with ammonium chloride, the expected products resulting from a conjugate addition. In the presence of copper(II) chloride intermediates 1–5 undergo dimerisation to yield the expected dimers.