Synthesis of Dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones via the Elusive Benzocyclobutenone Anion

We reported here a facile synthesis of dibenzo[a,e]cyclo-octene-5,11(6H,12H)-diones via dimerization of benzocyclobutenones in the presence of simple base via the elusive benzocyclobutenone anion-. The temperature effect played a crucial role in the dimerization reaction-. Further synthesis of 5,11-disubstituted dibenzo[ a , e ]cyclo-octenes (dibenzo[a,e][8]annulenes) from dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones was also explored.