Carbanion‐Induced Skeletal‐Rearrangements: From the Dibenzo[a,e] cyclooctene to the Indeno[2,1‐a]indene Framework

A surprising ring contraction to give derivatives 2 and 3 of indeno[2, 1-a]indene is observed in the reaction of 1 with organolithium compounds (R = alkyl, Ph; R1, R2 = H, alkyl, Ph). The expected nucleophilic substitution of 1 has so far only been accomplished in one case: with CuCN, the tetracarbonitrile 1, CN instead of Br, is formed.