Regioselective Borylation of Porphyrins by CH Bond Activation under Iridium Catalysis to Afford Useful Building Blocks for Porphyrin Assemblies

Harada, Hiroshi; Yamaguchi, Shigeru; Mori, Gorô; Nakazono, Satomi; Katoh, Taisuke; Takatsu, Keishi; Hiroto, Satoru; Shinokubo, Hiroshi; Osuka, Atsuhiro

doi:10.1002/asia.200700086

Cited by 74 publications

(60 citation statements)

References 144 publications

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“…Large TPA compounds attract considerable interest for several innovative applications such as threedimensional (3D) optical memory, deeper-penetrating photodynamic therapy (PDT) of cancer, 3D microfabrication, and others. [9] Diporphyrins 1 and 2 were prepared from b-borylated porphyrins 3 a and 3 b [10] (Scheme 1). Treatment of mono-and diborylporphyrins 3 a and 3 b with Oxone in a THF/acetone/ water suspension [11] successfully gave the corresponding mono-and dihydroxyporphyrins 4 a and 4 b in 80 % and 88 % yields, respectively.…”

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confidence: 99%

Synthesis of Doubly β‐to‐β 1,3‐Butadiyne‐Bridged Diporphyrins: Enforced Planar Structures and Large Two‐Photon Absorption Cross Sections

et al. 2007

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Covalently linked p-conjugated porphyrin oligomers are materials of great importance that display efficient energy and electron transfer, single-molecule conductivity, and nonlinear optical (NLO) properties.[1] Among them, peripherally ethyne-and 1,3-butadiyne-fabricated porphyrins hold a central position owing to their attractive electronic properties. [2][3][4][5] As representative examples, Therien and co-workers reported large hyperpolarizabilities for push-pull meso,-meso'-bis-arylethynylated porphyrins [3] and Anderson et al. reported large two-photon-absorption (TPA) properties of meso-ethyne-and meso-butadiyne-bridged porphyrin oligomers.[4] Most of the electronic properties of these conjugated porphyrins are considered to depend on the extent of overall p conjugation, which is a function of molecular coplanarity. However, there is a continuous distribution of rotational isomers because of small rotational barriers of triple-bond linkages [6] which duplicates their photophysics. [7] As an interesting approach, conformational control has been achieved with the aid of noncovalent interactions between a zinc porphyrin and a pyridine coordination site. [4b, 8] Herein, we report the synthesis of doubly b-to-b butadiyne-bridged diporphyrins as the first example of multiply 1,3-butadiyne-bridged diporphyrins. An apparent advantage of this double bridging strategy is a robust, enforced overall planar conformation, which causes significant enhancements of TPA properties. Large TPA compounds attract considerable interest for several innovative applications such as threedimensional (3D) optical memory, deeper-penetrating photodynamic therapy (PDT) of cancer, 3D microfabrication, and others. [9] Diporphyrins 1 and 2 were prepared from b-borylated porphyrins 3 a and 3 b[10] (Scheme 1). Treatment of mono-and diborylporphyrins 3 a and 3 b with Oxone in a THF/acetone/ water suspension [11] successfully gave the corresponding mono-and dihydroxyporphyrins 4 a and 4 b in 80 % and 88 % yields, respectively. The trifluoromethanesulfonyl derivatives were prepared in DMF by reaction with PhNTf 2 and Cs 2 CO 3 , [12] and following metallation with Zn(OAc) 2 6 aZn and 6 bZn were obtained in excellent yields. Installation of ethynyl groups was conducted through the standard Sonogashira coupling with trimethylsilylacetylene followed by desilylation to provide 8 aZn and 8 bZn in good yields. Then, 8 aZn and 8 bZn were subjected to a Cu II -mediated oxidative coupling reaction to furnish the corresponding butadiynebridged porphyrin dimers 1 Zn and 2 Zn in 82 % and 89 % yields, respectively. Demetallation with trifluoroacetic acid provided 1 H and 2 H in good yields. Synthesis of 1 Ni and 2 Ni was achieved in a similar fashion to 1 Zn and 2 Zn from Ni II triarylporphyrin as the starting material.b-to-b-Linked diporphyrins have been explored to examine the influences of connectivity difference on the electronic interactions between the porphyrins, [1e, 2a, 6a, 13, 14] but 2 H and its metal complexes (2 Zn and 2 Ni) are the fi...

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Synthesis of Doubly β‐to‐β 1,3‐Butadiyne‐Bridged Diporphyrins: Enforced Planar Structures and Large Two‐Photon Absorption Cross Sections

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“…This synthetic protocol has been further extended to the synthesis of phenanthroline‐fused porphyrin dimers (Scheme ). Suzuki–Miyaura cross‐coupling reaction of the 2‐borylated Ni II /porphyrin 11 Ni with 2,3‐diamino‐1,4‐dibromobenzene in a 2.5:1 ratio provided the β‐to‐β 1,4‐(2,3‐diamino)phenylene‐bridged Ni II /porphyrin dimer 12 Ni2 in 82 % yield. The condensation of 12 Ni2 with benzaldehyde under similar reaction conditions provided the phenanthroline‐fused Ni II /porphyrin dimer 13 Ni2 in 58 % yield.…”

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confidence: 99%

Pictet–Spengler Synthesis of Quinoline‐Fused Porphyrins and Phenanthroline‐Fused Diporphyrins

et al. 2016

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Doubly and quadruply quinoline‐fused porphyrins were effectively synthesized through a reaction sequence consisting of Suzuki–Miyaura coupling of β‐borylated porphyrins with 2‐iodoaniline and subsequent Pictet–Spengler cyclization. These quinoline‐fused porphyrins display red‐shifted absorption bands and higher electron‐accepting abilities. This synthetic protocol also allowed the synthesis of phenanthroline‐fused porphyrin dimers, which bound either a NiII or ZnII cation. The resultant metal complexes displayed further red shifted absorption spectra and molecular twists to effect an almost perpendicular arrangement of the two porphyrins.

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“…The aryl substituents instead of the porphyrin core can be selectively borylated. 21) For example, porphyrin tetramer 21 can be borylated exclusively on the methoxyphenyl groups to provide diborylated product 22 because 21 has accessible C–H bonds only on the terminal aryl substituents (Scheme 12). This procedure would be useful for terminal selective functionalization of molecular wires.…”

Section: Introductionmentioning

confidence: 99%

Transition metal catalyzed borylation of functional π-systems

Shinokubo

2014

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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Borylated functional π-systems are useful building blocks to enable efficient synthesis of novel molecular architectures with beautiful structures, intriguing properties and unique functions. Introduction of boronic ester substituents to a variety of extended π-systems can be achieved through either iridium-catalyzed direct C–H borylation or the two-step procedure via electrophilic halogenation followed by palladium-catalyzed borylation. This review article focuses on our recent progress on borylation of large π-conjugated systems such as porphyrins, perylene bisimides, hexabenzocoronenes and dipyrrins.

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Regioselective Borylation of Porphyrins by CH Bond Activation under Iridium Catalysis to Afford Useful Building Blocks for Porphyrin Assemblies

Cited by 74 publications

References 144 publications

Synthesis of Doubly β‐to‐β 1,3‐Butadiyne‐Bridged Diporphyrins: Enforced Planar Structures and Large Two‐Photon Absorption Cross Sections

Synthesis of Doubly β‐to‐β 1,3‐Butadiyne‐Bridged Diporphyrins: Enforced Planar Structures and Large Two‐Photon Absorption Cross Sections

Pictet–Spengler Synthesis of Quinoline‐Fused Porphyrins and Phenanthroline‐Fused Diporphyrins

Transition metal catalyzed borylation of functional π-systems

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