Carbazole Based Smaragdyrins: Synthesis, Aromaticity Switching, and Formation of a Spiro‐Dimer

Abstract Carbazole‐incorporated smaragdyrin BF 2 ‐complex 3 was synthesized by S N Ar reaction of 3,5‐dibromo‐8‐mesityl‐BODIPY 1 with 3,6‐di( tert ‐butyl)‐1,8‐di(pyrrol‐2‐yl)carbazole 2 as a nucleophile. Demetalation of 3 with ZrCl 4 gave the corresponding smaragdyrin free base 4 in a good yield. Oxidations of 3 and 4 with MnO 2 gave smaragdyrins 5 and 6 , respectively, both followed by aromaticity switching, since the oxidized products showed a moderate paratropic ring current owing to their 20π‐electronic circuits. Further, treatment of 4 with [RhCl(CO) 2 ] 2 in the presence of NaOAc gave Rh I complex 7 , and oxidation of 3 with RuCl 3 in the presence of triethylamine led to the formation of a spiro dimer product, 8 .