2,3‐Dilithio‐1,3‐butadienes via Addition of Lithium to Butatrienes

The Butatrienes 1 add lithium to the central double bond to give the dilithiobutadienes 2 (over 95% yield). These are not only of theoretical interest but are also suitable as synthetic building blocks (addition of electrophiles). Upon reaction with an excess of lithium in the presence of HgCl2 they undergo cleavage with formation of 1,1-dilithio-1-alkenes 3.