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

Abstract

Naphthalene- and phenanthrene-fused [22]smaragdyrin BF₂ -complexes were synthesized by 1) Suzuki-Miyaura coupling of β-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.

Keywords: antiaromaticity; aromaticity; fusion; smaragdyrin; vinyl ether.