Singly and Doubly Neo-Confused Smaragdyrins

Smaragdyrin had been an important but elusive expanded porphyrin until our recent first synthesis (Xie et al., J. Am. Chem. Soc. 2018, 140, 16553). In this paper, we report the synthesis of singly and doubly neo-confused [22]­smaragdyrin BF2-complexes 13 and 15 both as stable smaragdyrin mutants by nucleophilic substitution reactions of 1,9-dibromo-5-mesityldipyrrin 1 with singly and doubly N-confused tripyrranes, 10 and 11, respectively. Demetalation of 13 and 15 with methanesulfonic acid furnished singly and doubly neo-confused [22]­smaragdyrin free bases 16 and 18, respectively, both as air-sensitive porphyrinoids. These neo-confused [22]­smaragdyrin free bases display characteristic properties such as decreased diatropic ring current, regioselective diprotonation at the inner α-carbon of the neo-confused pyrrole to give 16H22+ and 18H22+, and smooth oxygenation at the inner α-position of the neo-confused pyrroles, giving neo-confused [22]­oxosmaragdyrin 17 and doubly neo-confused [24]­dioxosmaragdyrin Cu­(II) complex 19Cu via metalation of 18 with CuCl2 in the presence of NaOAc. Finally, demetalation of 19Cu with methanesulfonic acid gave the corresponding doubly neo-confused [24]­dioxosmaragdyrin 19

Singly and Doubly Neo-Confused Smaragdyrins

Smaragdyrin had been an important but elusive expanded porphyrin until our recent first synthesis (Xie et al., J. Am. Chem. Soc. 2018, 140, 16553). In this paper, we report the synthesis of singly and doubly neo-confused [22]­smaragdyrin BF2-complexes 13 and 15 both as stable smaragdyrin mutants by nucleophilic substitution reactions of 1,9-dibromo-5-mesityldipyrrin 1 with singly and doubly N-confused tripyrranes, 10 and 11, respectively. Demetalation of 13 and 15 with methanesulfonic acid furnished singly and doubly neo-confused [22]­smaragdyrin free bases 16 and 18, respectively, both as air-sensitive porphyrinoids. These neo-confused [22]­smaragdyrin free bases display characteristic properties such as decreased diatropic ring current, regioselective diprotonation at the inner α-carbon of the neo-confused pyrrole to give 16H22+ and 18H22+, and smooth oxygenation at the inner α-position of the neo-confused pyrroles, giving neo-confused [22]­oxosmaragdyrin 17 and doubly neo-confused [24]­dioxosmaragdyrin Cu­(II) complex 19Cu via metalation of 18 with CuCl2 in the presence of NaOAc. Finally, demetalation of 19Cu with methanesulfonic acid gave the corresponding doubly neo-confused [24]­dioxosmaragdyrin 19

Bottom-Up Synthesis of Multiply Fused Pd^II Anthriporphyrinoids

Anthriporphyrinoid and its dimeric homologues were synthesized by Suzuki–Miyaura coupling and subsequent oxidation. Both porphyrinoids were smoothly converted to their PdII complexes and were further decorated by Suzuki–Miyaura coupling with thiophene derivatives and subsequent oxidative fusion reaction to provide multiply fused compounds. Most PdII anthriporphyrinoids have been structurally well characterized to be planar for monomeric and helically twisted for dimeric species. The dimeric anthriporphyrinoids show paratropic ring currents due to their global antiaromatic networks, the extent of which increases with an increase of conjugated network. Multiply fused dimeric anthriporphyrinoids show helical structures, fully reversible six redox potentials, small HOMO–LUMO gaps, and absorption tails reaching in the near-infrared region, suggesting the high potential of this approach to explore molecular graphene. Optical separations of the dimeric helical species were accomplished, and racemization barrier heights were determined

B^III–Subporphyrins Bearing Distorted Metal-Coordinating Straps: Cu^II-Assisted <i>meso</i>-Fabrications

BIII-subporphyrins 4, 5, and 6 possessing metal-coordinating carbaporphyrin-like pockets were synthesized by Suzuki–Miyaura coupling reactions. Compounds 4 and 5 gave PdII complexes 4-Pd and 5-Pd upon metalation with Pd(OAc)2 but did not give either their NiII or CuII complexes. Conversely, 6 was expected to induce distorted square planar coordination because of its 2,5-di(pyrid-2-yl)pyrrole strap. Indeed reaction of 6 with Cu(OAc)2 did not give its CuII complex but produced meso-alkoxy and meso-phenoxy products in the presence of alcohols and phenol, possibly via CuII-mediated C–H bond functionalization, which was further extended to meso-C–C bond-forming fabrications by using organoboronic acids. These CuII-mediated C–H bond meso-fabrications are the first example for porphyrinoid substrates

Rhodium-Catalyzed [5 + 2] Annulation of Pyrrole Appended BODIPYs: Access to Azepine-Fused BODIPYs

Rhodium-catalyzed C–H/N–H [5 + 2] annulations of 8-(pyrrol-2-yl)-appended boron-complexed dipyrromethenes (BODIPYs) with internal alkynes have been established to afford a series of azepine-fused BODIPYs with good yields and excellent regioselectivity, in which the pyrrol-2-yl unit serves as the directing group as a rare example. A RhI intermediate was obtained to indicate a RhI/RhIII catalytic process involved in this reaction. Importantly, the [5 + 2] C–H annulation is demonstrated as a concise strategy to change the optical properties of BODIPY

Stable Antiaromatic [24]Hexaphyrin(1.1.0.0.1.0) and Its Metal Complexes

5,10,23-Trimesityl-substituted [24]hexaphyrin(1.1.0.0.1.0) was synthesized as a stable antiaromatic molecule by base-catalyzed twofold SNAr reaction and was reduced to the corresponding [26]hexaphyrin, which was an unstable aromatic molecule because it easily oxidized to the [24]hexaphyrin. The [24]hexaphyrin served as a ligand to give the bis-PdII complex and tris-RhI complex with unique structures. The former complex has two square-planar-coordinated PdII ions bridged by an acetate anion and shows a strong paratropic ring current, while the latter complex has three RhI ions coordinated with two pyrrolic nitrogen atoms and two carbonyl groups, but one carbonyl group is shared with two RhI ions in a unique manner

Copper(II) Carbaporphyrins: Oxygenation Reactivities Dependent upon Coordinating Structures

CuII metalations of carbaporphyrins 1–4 gave the corresponding CuII complexes 1-Cu, 2-Cu, 3-Cu, and 4-Cu with varying degrees of distortions in CuII square-planar coordination. Upon treatment with Cu­(OAc)2, 1-Cu was inert but 2-Cu and 3-Cu gave the respective O-atom-inserted complexes 2-OCu and 3-OCu. Further, 3-Cu and 4-Cu were converted to meso-methoxynickel­(II) porphyrins 3-OMe and 4-OMe, respectively, via treatment with Cu­(OAc)2 in methanol. meso-Hydroxynickel­(II) porphyrin 3-OH was obtained by the treatment of 3-OCu by acetic acid. The treatment of 4-Cu with Cu­(OAc)2 in the presence of acetic acid gave 5,15-diketoporphyrinogen 4-O. CuII complexes of carbaporphyrins became more reactive with an increased distortion in CuII square-planar coordination

Confusion Approach Modulated Syntheses of Corrorin Parasitized Hexaphyrins(1.1.1.1.1.0) and the Oxidative Ring Cleavage Behavior

A corrorin parasitized hexaphyrin(1.1.1.1.1.0) 1 was synthesized by [4 + 4] condensation, and subsequent treatment with PbO2 afforded hexaphyrin 2 appended with a dipyrrinone moiety via regioselective opening of the corrorin ring. In contrast, oxidation of the corresponding corrorin–N-confused hexaphyrin(1.1.1.1.1.0) hybrid 3 afforded only a keto adduct 4. As a result, the planarity and aromaticity of the hexaphyrin moiety can be modulated

<i>meso</i>-Triaryl-Substituted Smaragdyrins: Facile Aromaticity Switching

All-aza smaragdyrin, a historic but elusive pentapyrrolic macrocycle, was successfully synthesized and characterized for the first time. [22]­Smaragdyrin BF2-complex 3 was smoothly synthesized by 2-fold SNAr reaction of 1,9-dibromo-5-mesityldipyrrin with 5,10-dimesityltripyrrane. Treatment of 3 with methanesulfonic acid gave [20]­smaragdyrin 5 as a stable antiaromatic compound. Reduction of 5 with NaBH4 under inert conditions gave [22]­smaragdyrin 6 as an aromatic congener, which was easily oxidized back to 5 in the air. Complex 3 was interconvertible with its 20π-congener 4 via oxidation with MnO2 and reduction with NaBH4. Treatment of 3 or 4 with CuCl2 in the presence of NaOAc gave hetero bimetal complex 8

<i>meso</i>-Triaryl-Substituted Smaragdyrins: Facile Aromaticity Switching

All-aza smaragdyrin, a historic but elusive pentapyrrolic macrocycle, was successfully synthesized and characterized for the first time. [22]­Smaragdyrin BF2-complex 3 was smoothly synthesized by 2-fold SNAr reaction of 1,9-dibromo-5-mesityldipyrrin with 5,10-dimesityltripyrrane. Treatment of 3 with methanesulfonic acid gave [20]­smaragdyrin 5 as a stable antiaromatic compound. Reduction of 5 with NaBH4 under inert conditions gave [22]­smaragdyrin 6 as an aromatic congener, which was easily oxidized back to 5 in the air. Complex 3 was interconvertible with its 20π-congener 4 via oxidation with MnO2 and reduction with NaBH4. Treatment of 3 or 4 with CuCl2 in the presence of NaOAc gave hetero bimetal complex 8