Base-controlled 1,6-enyne-bicyclization: divergent synthesis of benzo[b]fluorenones and benzo[b]fluorenols

Abstract An interesting base-controlled protocol for the divergent and atom-economic synthesis of benzo[ b ]fluorenones and benzo[ b ]fluorenols with the great diversity in substitution patterns has been developed. Started from readily available 1,6-enynes, good to excellent yields of the corresponding tetracyclic benzo[ b ]fluorenones and benzo[ b ]fluorenols can be chemoselectively achieved under metal-free conditions. Notably, only K 2 CO 3 or Et 3 N was required as the promoter here and the reaction can work well in a high-selective manner.