Conjugate Additions of Organolithiums to Electron-poor Olefins: A Simple and Useful Approach to the Synthesis of Complex Molecules

Conjugate addition reactions of organometallic compounds to electron-poor olefins is a versatile synthetic methodology for the formation of new carbon–carbon bonds. However, a careful control of the regioselectivity of the process is needed because of the presence of two electrophilic sites in the activated olefin. This issue is often overcome by employing "soft" nucleophiles such as organocopper and organozinc reagents, because of their high selectivity towards the 1,4-addition. In contrast, organolithium compounds, which are "hard" nucleophiles, generally give access to 1,2-adducts, 1,4-conjugate addition being sometimes observed according to the nature of nucleophiles and/or electrophiles, or to the presence of additives. In this Minireview, we have described some peculiar examples to get an outline of the recent acquisitions in the field of the conjugate additions of functionalized organolithiums to electron-poor olefins. Particular attention is paid to the synthesis of complex structures starting from simple substrates by means of cascade reactions promoted by conjugate addition reactions with organolithiums. Dedicated to the memory of Professor José Barluenga.