Facile Carbolithiation of Bent Alkyne without Catalyst. Tandem Route to Dibenzo[b,f]pentalenes from Dibenzocyclooctadiyne

Nucleophilic addition of RLi to a triple bond of dibenzocycloocta[a,e]diyne provides dibenzo[b,f]pentalene motif through trans-annulation of the resulting vinyllithium. Dibenzopentalene anion thus formed reacts with various electrophiles such as aldehydes, alkyl halides, acid halide, and Me3SiCl to give the corresponding products.