intramolecular [4 + 2] cycloaddition to give benzo[b]fluorene derivatives in good yields. The hybridization of the tether connecting the reacting alkynes has a pronounced effect on the course of the reaction. Theoretical calculations and isotopic labeling studies support a mechanism which involves the generation of a cyclic allene intermediate that evolves to the final benzo[b]fluorene.
Non-conjugated benzotriynes 2 undergo a novel radical cycloaromatization to provide the benzo[b]fluorenecore of the kinamycins. The overall process involves a thermal intramolecular cyclization to the non-benzenoid biradicals 4 followed by radical cyclization and hydrogen abstraction.
非共轭苯并三炔2进行新颖的自由基环芳构化,以提供那那霉素的苯并[ b ]芴核。整个过程包括热分子内环化为非苯并双基4,然后进行自由基环化和氢提取。