Synthesis of Naphthalene- and Phenanthrene-Fused Smaragdyrins and Their BF2 Complexes

Naphthalene- and phenanthrene-fused [22]smaragdyrin BF2-complexes were synthesized by 1) Suzuki-Miyaura coupling of beta-brominated [22]smaragdyrin BF2 complexes with 2-formylarylboronates, 2) Witting-type methoxymethylenation of the formyl group, and 3) methanesulfonic acid-catalyzed cyclization reaction. Subsequently these BF2 complexes were deboronized and oxidized to the corresponding antiaromatic [20]smaragdyrin free bases. The installed fused structures led to decrease of the aromatic characters of the [22]smaragdyrin BF2 complexes and the antiaromatic characters of the [20]smaragdyrin free bases.