m‐Pyrenisubporphyrins and Their BIII Complexes and Reduced Congeners

m-Pyrenisubporphyrins were synthesized and converted to B^III complexes, from which oxygen-atom-inserted product was formed upon heating in the air. Reductions of m-pyrenisubporphyrin with p-tosylhydrazide and K₂CO₃ gave m-pyrenisubchlorin and m-pyrenisubbacteriochlorin in good yields.

Abstract

m-Pyrenisubporphyrins were synthesized by Pd-catalyzed cross-coupling of α,α’-diboryl-m-pyrenitripyrrane with 9,10-bis(1,1-dibromomethylenyl)anthracene followed by oxidation with DDQ. Reaction of the m-pyrenisubporphyrin with BBr₃ and triethylamine gave a B-hydroxy complex and an oxygen-atom-inserted product. Reaction of the m-pyrenisubporphyrin with PhBCl₂ and triethylamine gave a B-phenyl complex. These m-pyrenisubporphyrins show red-shifted absorption bands, reflecting the incorporated pyrene segment, but are all nonaromatic. Reduction of m-pyrenisubporphyrin with p-tosylhydrazide and K₂CO₃ gave m-pyrenisubchlorin and m-pyrenisubbacteriochlorin, depending upon the reaction conditions. These reduced products have also been shown to be nonaromatic by the low-field shifted chemical shifts of the inner pyrrolic protons, broad and non-structured absorption bands, and small NICS values.

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