The Desulfurization of Polynuclear Aromatic Sulfur Compounds with a Raney Nickel

Nagai, Masatoshi; Urimoto, Hideo; Uetake, Kazuya; Sakikawa, Noriyuki; Gonzalez, Richard

doi:10.1246/bcsj.62.557

Cited by 11 publications

(3 citation statements)

References 21 publications

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“…We then examined the reductive desulfurization of meso‐thienyl‐substituted subporphyrins. A solution of 1 b in toluene was treated with W‐7 Raney Nickel7 at 40 °C for 30 min, and TLC analysis confirmed the consumption of 1 b . Comparison of the 1 H and 11 B NMR spectra of the reaction mixture with those of meso‐triaryl‐substituted counterparts indicated the formation of meso ‐ tripentylsubporphyrin 1 b , along with several over‐reduced products (see the Supporting Information) 1c.…”

Section: Methodsmentioning

confidence: 99%

Meso‐Trialkyl‐Substituted Subporphyrins

et al. 2009

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In recent years, subporphyrins, which are ring-contracted porphyrins, have emerged as promising functional molecules because of their attractive features, including bowl-shaped structures, 14p-electronic aromatic systems, porphyrinlike spectral characteristics, intense fluorescence, and supramolecular chemistry based on axial chelation of the boron atom. [1][2][3] Notably, the free rotation of meso-aryl substituents of subporphyrins leads to the large electronic effects that give rise to highly perturbed optical properties, as demonstrated by oligo-1,4-phenyleneethynylene and 4-aminophenyl substituted subporphyrins. [4] Despite this progress, the chemistry of subporphyrins still remains in its infancy and an effective synthetic entry into novel subporphyrins is highly desirable. Considering the important roles that meso-alkyl-substituted porphyrins have played in the development of porphyrin chemistry since the first porphyrin synthesis in 1935, [5] it is desirable to study the chemistry of meso-trialkyl-substituted subporphyrins, but the synthesis of this class of molecules has not been reported to date. Herein, we report the first synthesis of meso-trialkyl-substituted subporphyrins.We initially applied our synthetic protocol for mesotriaryl-substituted subporphyrin [1c] to the synthesis of mesotrialkyl-substituted subporphyrins. Pyridine-tri-N-pyrrolylborane was condensed with 1-pentanal under various reaction conditions by changing reaction parameters such as solvent, temperature, molar ratio, and any possible additives. Unfortunately, the desired meso-tributyl subporphyrin was not detected. These negative results led us to explore an indirect route that involved the synthesis of meso-thienyl subporphyrins, and subsequent reductive desulfurization with Raney nickel. Thus, subporphyrins 1 a and 1 b were prepared by using our protocol in 1.7 and 3.7 % yield, respectively (Scheme 1).The higher yield of 1 b may be ascribed to the absence of the free a-thienyl position, since free a-thiophenes are prone to oxidative degradation. It is noteworthy that these compounds are the first examples of subporphyrins that bear fivemembered aromatic heterocycles. Single-crystal X-ray diffraction analysis revealed the bowl-shaped structure of 1 b (Figure 1), in which the dihedral angles [6] of the meso-thienyl substituents are all small (31.7, 35.6, and 48.28), thus allowing the strong electronic conjugation of these substituents with the subporphyrin core. These dihedral angles are slightly smaller than those of meso-triphenyl subporphyrin 3 (38.3, 45.7, and 48.18), which reflect the compact size of the mesothienyl substituents. Scheme 1. Synthesis of meso-trialkylsubporphyrins 2 a-c.Figure 1. X-ray crystal structure of subporphyrin 1 b (thermal ellipsoids are set at the 50 % probability level).

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Section: Methodsmentioning

confidence: 99%

Meso‐Trialkyl‐Substituted Subporphyrins

et al. 2009

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“…Because acid-mediated synthesis of subporphyrins 9 did not proceed with aliphatic aldehydes, thiophene-2-carbaldehyde was used as a pentanal equivalent through Ni-mediated desulfurization. 10,11 In general, breaking a thiophene ring into a saturated alkane can be useless in most cases from the viewpoint of organic synthesis, while desulfurization is an important industrial process in oil refinery. 12 The chemical equation in the handout inspired H.Y.…”

Section: Account Syn Lettmentioning

confidence: 99%

Aromatic Metamorphosis of Dibenzothiophenes

Yorimitsu

Vasu

Bhanuchandra

et al. 2016

Synlett

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In general, aromatic cores are stable owing to their resonance energies. Different from facile peripheral modifications of aromatic cores, transforming an aromatic core into a different skeleton is ambitious and has attracted only little attention as a general synthetic method. This personal account shows our journey to inventing transformations of dibenzothiophenes into triphenylenes, carbazoles, and spirocyclic diarylfluorenes and to establishing 'aromatic metamorphosis' as a useful and game-changing strategy in organic synthesis. 1 Introduction 2 Aromatic Metamorphosis 3 From Dibenzothiophenes to Triphenylenes 4 From Dibenzothiophenes to Carbazoles 5 From Dibenzothiophenes to Spirocyclic Tetraarylmethanes 6 Conclusion

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“…A solution of 1 b in toluene was treated with W-7 Raney Nickel [7] at 40 8C for 30 min, and TLC analysis confirmed the consumption of 1 b. Comparison of the 1 H and 11 B NMR spectra of the reaction mixture with those of meso-triaryl-substituted counterparts indicated the formation of meso-tripentylsubporphyrin 1 b, along with several over-reduced products (see the Supporting Information).…”

mentioning

confidence: 98%

Meso‐Trialkyl‐Substituted Subporphyrins

et al. 2009

View full text Add to dashboard Cite

In recent years, subporphyrins, which are ring-contracted porphyrins, have emerged as promising functional molecules because of their attractive features, including bowl-shaped structures, 14p-electronic aromatic systems, porphyrinlike spectral characteristics, intense fluorescence, and supramolecular chemistry based on axial chelation of the boron atom. [1][2][3] Notably, the free rotation of meso-aryl substituents of subporphyrins leads to the large electronic effects that give rise to highly perturbed optical properties, as demonstrated by oligo-1,4-phenyleneethynylene and 4-aminophenyl substituted subporphyrins.[4] Despite this progress, the chemistry of subporphyrins still remains in its infancy and an effective synthetic entry into novel subporphyrins is highly desirable. Considering the important roles that meso-alkyl-substituted porphyrins have played in the development of porphyrin chemistry since the first porphyrin synthesis in 1935, [5] it is desirable to study the chemistry of meso-trialkyl-substituted subporphyrins, but the synthesis of this class of molecules has not been reported to date. Herein, we report the first synthesis of meso-trialkyl-substituted subporphyrins.We initially applied our synthetic protocol for mesotriaryl-substituted subporphyrin [1c] to the synthesis of mesotrialkyl-substituted subporphyrins. Pyridine-tri-N-pyrrolylborane was condensed with 1-pentanal under various reaction conditions by changing reaction parameters such as solvent, temperature, molar ratio, and any possible additives. Unfortunately, the desired meso-tributyl subporphyrin was not detected. These negative results led us to explore an indirect route that involved the synthesis of meso-thienyl subporphyrins, and subsequent reductive desulfurization with Raney nickel. Thus, subporphyrins 1 a and 1 b were prepared by using our protocol in 1.7 and 3.7 % yield, respectively (Scheme 1).The higher yield of 1 b may be ascribed to the absence of the free a-thienyl position, since free a-thiophenes are prone to oxidative degradation. It is noteworthy that these compounds are the first examples of subporphyrins that bear fivemembered aromatic heterocycles. Single-crystal X-ray diffraction analysis revealed the bowl-shaped structure of 1 b (Figure 1), in which the dihedral angles [6] of the meso-thienyl substituents are all small (31.7, 35.6, and 48.28), thus allowing the strong electronic conjugation of these substituents with the subporphyrin core. These dihedral angles are slightly smaller than those of meso-triphenyl subporphyrin 3 (38.3, 45.7, and 48.18), which reflect the compact size of the mesothienyl substituents.Scheme 1. Synthesis of meso-trialkylsubporphyrins 2 a-c. Figure 1. X-ray crystal structure of subporphyrin 1 b (thermal ellipsoids are set at the 50 % probability level).

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The Desulfurization of Polynuclear Aromatic Sulfur Compounds with a Raney Nickel

Cited by 11 publications

References 21 publications

Meso‐Trialkyl‐Substituted Subporphyrins

Meso‐Trialkyl‐Substituted Subporphyrins

Aromatic Metamorphosis of Dibenzothiophenes

Meso‐Trialkyl‐Substituted Subporphyrins

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