From 21,23‐Dioxaporphyrin to a 3‐Pyranone Dioxacorrole Skeleton: The Achmatowicz Rearrangement in the Porphyrin Frame

Abstract

Be independent: Under basic conditions a furan ring entrapped in an aromatic macrocycle readily recovered the properties characteristic for a free molecule and assimilated a water molecule forming the Achmatowicz rearrangement product with a 3‐pyranone subunit built in. Coordination of palladium(II) created a complex stabilizing the second tautomer with two sp3 carbon atoms (oxygen red, water green, palladium purple, and the aryl group blue).

Reversible Reduction of Oxatriphyrin(3.1.1)—Adjusting the Coordination Abilities to the Central Ion

“…The reactivity of the furan ring, widely applied in organic synthesis, has remained almost untouched in the porphyrinoidal skeletons, limited to the O→N, S, Se exchange reactions reported by Vogel and co‐workers 12. Nevertheless such reactivity opens paths for postsynthetic modifications of the macrocycle leading to architectures unavailable by any other approach, as we have recently reported the formation of an oxatriphyrin(4.1.1) from 21,23‐dioxaporphyrin via the Achmatowicz rearrangement 13. The structural factors described for 6 are conserved in 7 (i.e., sp 3 C(3) carbon observed at 87 ppm), but two additional tetrahedral carbon atoms were identified ( 13 C chemical shifts C(1 1 ) 107.6 and C(2 1 ) 105.7 ppm) reflecting the formation of geminal ethers derived from furan by oxidation and substitution 11.…”

A Parallel‐Displaced Directly Linked 21‐Carba‐23‐Thiaporphyrin Dimer Incorporating a Dihydrofulvalene Motif

“…The H(2')and H(3')protons afford multiplets significantly shifted upfield at À0.5 and À1.85 ppm, correspondingly.F urther 13 C characterization has shown the presence of three tetrahedral C(21), C(2')a nd C(3')c arbon atoms (d = 45.5, 61.6 and 46.6 ppm, respectively), what is in agreement with the structure of 8H + .T he indirect evidence of the presence of substituents involving oxygen at the C(2')a nd C(21')a toms was proved by 1 H-13 CH MBC experiment showing appropriate 13 Cc hemical shifts at 61.6 and 167.5 ppm as ar esult of substitution by more electronegative hydroxyl and the presence of carbonyl group,r espectively. [14] Thef ormation of 8 was confirmed by high resolution mass spectrometry (m/z calcd for [MÀOH] + :1139[MÀOH] + : .4756, found:1139.…”

Möbius Aromatic Core‐Modified Heterocyclic [20] Macrocycles (4.1.1) with a Protruding N‐Methyl Pyrrole Ring

“…Herein, we reporto ur first efforts towardst he rational synthetic design and synthesis of an unprecedented tripyrrane moiety (5), which has led to the isolation of two hitherto-unknown [20] aromatic macrocycles 8 and 9.T hese macrocycles have been synthesized by strategically bringing b,b-carbon atoms of N-methyl pyrrole ring into the core of the macrocycles. [6] To synthesize the target macrocycles, we designed the three-step synthesisof (1-methyl-1H-pyrrole-3,4-diyl)bis(phenylmethanone) (3;S cheme 1) from pyrrole, in whichb ulky substituentso nt he nitrogen atom of the pyrrole moiety were employedt oo bstructe lectrophilica ttack at the a positions through significant steric and electronic effects. In this context, the report by Corey et al [7a] was highly impactful, sparkingt he idea that triisopropylsilyl (TIPS)-pyrrole could act as ap rogenitor of b-substituted pyrrole 3 through kinetic electrophilics ubstitutiono f1 -(triisopropylsilyl) pyrrole.…”