Homologation of Heterocycles by a Sequential Reductive Opening Lithiation–Electrophilic Substitution–Cyclization

Functionalised organolithium compounds by sulfur-lithium exchange

Multifunctional organic molecules can be accessed by reacting functionalised organolithium compounds (they can be prepared following a great number of different methodologies) with electrophilic reagents, this fact makes these intermediates of relevant interest in synthetic organic chemistry. Sulfur containing molecules have been used extensively as precursors of organolithium compounds by applying two different methodologies. One is the well-known alpha-deprotonation, which is not going to be the subject of this review, and the other methodology consists of sulfur lithium exchange by using lithium metal either alone or in the presence of a stoichiometric or catalytic amount of an arene. In some special cases, for instance in gem-dithio- or 1,1,1-trithiosubstituted compounds, sulfur lithium exchange can be performed by means of an alkyllithium reagent. The following tutorial review is ordered on the basis of the relative position of the functional group and the carbanionic center, with special mention to the application of these intermediates in organic synthesis.