Cohen Reductive Lithiation

The Cohen reductive lithiation is the formation of organic lithium compound by reductive lithiation of phenyl thioethers with aromatic radical anions, and the formed organic lithium compound can react with electrophiles to produce a variety of molecules. Various aromatic radical anions have been used. Besides the phenyl‐thioethers, several other molecules are reduced by the above aromatic radical anions. This method is also involved in the preparation of allylsilane, 1,3‐diol, highly crowd amines (from α‐amino nitriles), butenyl alcohol (via sigmatropic [2,3] rearrangement), and especially the five‐membered carbocycles via the anionic cyclization with good stereoselectivity. The aromatic radical anions have been found to be generated in tetrahydrofuran (THF). The dimethyl ether (DME) is found suitable in LDMAN for the generation of such anions. During the reductive lithiation of tetrahydrofurans and tetrahydropyrans, the epimers predominantly give the axial lithio derivative.