Rational Synthesis of 5,5,5‐Tricyclic Fused Thia‐heptaphyrin (1.1.1.1.1.1.0) From a Helical Oligopyrrin Hybrid

Abstract

Oxidation of a thiophene-hexapyrrane hybrid S-P 6 afforded a stable conjugated open-chain thiaheptapyrrolic helix 1 with the terminal thiophene and confused pyrrole units lying at a long distance that is adverse for further cyclization. Chelation of 1 with copper(II) ion afforded 1-Cu, which exhibits more distant terminal units. Interestingly, further oxidation of 1 triggered an intramolecular CÀ N fusion reaction to afford a unique 5,5,5-tricyclic fused linear thiaheptapyrrin 2, with the two terminals positioned in proximity, which favors the oxidative ring-closure reaction to give a unique 5,5,5-tricyclic fused thiaheptaphyrin (1.1.1.1.1.1.0) 3 under air. The inner-fusion strategy for positioning the reactive sites in proximity to promote oxidative cyclization offers a new approach for constructing large porphyrinoids through conjugated oligopyrrins without the assistance of metal ions.

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…A fused thiaheptaphyrin(1.1.1.1.1.1.0) 381.3a , structurally related to 380.2 , was obtained by sequential dehydrogenation of a heptapyrromethane analogue ( Scheme 381 ). 748 In the solid state, the brominated derivative 381.3b was found to contain a pyrrolo[3,2- b ]pyrrolizine fragment and to adopt a figure-eight-like conformation. The UV–vis–NIR spectrum of 381.3a in DCM displayed absorption maxima at 428, 653, and 808 nm and a broad low-energy band at 950–1350 nm.…”

Advances in the Synthesis of Benzo‐Fused Spiro Nitrogen Heterocycles: New Approaches and Modification of Old Strategies

“…[36,37] The topic of spiro-fused heterocycles is quite wide and therefore often touched upon when studying the chemistry of natural compounds, [38,39] in review articles [40] on the use of individual organic compounds in the synthesis of alkaloids, [41] in the enantioselective synthesis of hetero and carbocycles [42] or their macrocyclic analogs. [43,44] There are cases that deserve our attention when the formation of certain alkaloids passes through the stage of metastable spiroheterocyclic intermediates generation. [45] Compounds containing a spiro carbon center were also obtained biosynthetically.…”

“…These studies have been presented to the chemical community in original articles, [1–26] in thematic reviews, [27–35] as well as in review articles on the synthesis of some other heterocycles where spiro analogs are mentioned in one way or another [36,37] . The topic of spiro‐fused heterocycles is quite wide and therefore often touched upon when studying the chemistry of natural compounds, [38,39] in review articles [40] on the use of individual organic compounds in the synthesis of alkaloids, [41] in the enantioselective synthesis of hetero and carbocycles [42] or their macrocyclic analogs [43,44] …”