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Nozoe, Tetsuo; Seto, S.; Takase, Kahei; MATSUMURA, Shingo; Nakazawa, Tomoo

doi:10.1246/nikkashi1948.86.346

Cited by 16 publications

(8 citation statements)

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“…The synthesis of a 1,3-substituted 2,6-diisocyanoazulene from 2-amino-1,3-diethoxycarbonylazulene, 1, in a 57% cumulative yield is summarized in Scheme 1. After bromination of 1 exclusively at position 6, 20 the azulenic moiety was activated toward nucleophilic substitution by converting amine 2 into formamide 3. Treatment of 3 with NaN 3 gave azide 4.…”

Section: Resultsmentioning

confidence: 99%

“…This procedure is based on that of Nozoe et al . Bromine (3.84 g, 24.0 mmol) was added dropwise to a chilled (0 °C) solution of 2-amino-1,3-diethoxycarbonylazulene (6.90 g, 24.0 mmol) in 250 mL of chloroform with vigorous stirring over a period of 20 min. The ice bath was then removed, and the reaction mixture was allowed to warm to room temperature.…”

Section: Methodsmentioning

confidence: 99%

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The 2,6-Diisocyanoazulene Motif: Synthesis and Efficient Mono- and Heterobimetallic Complexation with Controlled Orientation of the Azulenic Dipole

Holovics

Robinson²,

Weintrob³

et al. 2006

J. Am. Chem. Soc.

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Synthesis of the remarkably air- and thermally stable 2,6-diisocyano-1,3-diethoxycarbonylazulene linker from 2-amino-1,3-diethoxycarbonylazulene in 57% cumulative yield was developed. Incorporation of the ester "arms" in the design of this first diisocyanoazulene bridge permitted fully controlled stepwise installation and complexation of its isocyano junction groups. The -CO(2)Et arms in 2,6-diformamido-1,3-diethoxycarbonylazulene effectively suppress the rate of dehydration of its 2-NHCHO end relative to that of the 6-NHCHO end leading to practically exclusive formation of 6-isocyano-2-formamido-1,3-diethoxycarbonylazulene upon treatment of the above diformamide with an equimolar amount of POCl(3). This crystallographically characterized 6-isocyano-2-formamidoazulene derivative was employed to access mono- and heterobimetallic complexes of the 2,6-diisocyanoazulene scaffold with controlled orientation of the azulenic dipole. A complete series of monometallic, homobimetallic, and isomeric heterobimetallic ([M] = M(CO)(5), M = Cr and/or W) complexes of the 2,6-diisocyanoazulene motif was isolated and studied by a variety of techniques, including X-ray crystallography. The metal-to-bridge charge transfer in mono- and dinuclear adducts of 2,6-diisocyanoazulene, the assignment of which was corroborated by time-dependent density functional theory calculations, occurs at a dramatically lower energy as compared to the analogous systems featuring the 1,4-diisocyanobenzene scaffold. Moreover, the metal-to-diisocyanide charge transfer exhibits a substantially greater red shift upon binucleation of the mononuclear [M(CO)(5)] adducts of the nonbenzenoid 2,6-diisocyanoazulene linker versus the 1,4-diisocyanobenzene bridge.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The 2,6-Diisocyanoazulene Motif: Synthesis and Efficient Mono- and Heterobimetallic Complexation with Controlled Orientation of the Azulenic Dipole

Holovics

Robinson²,

Weintrob³

et al. 2006

J. Am. Chem. Soc.

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“…Tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one) is a nonbenzenoid aromatic compound having a flat seven-membered ring that shows cycloheptatrienylium ion character. The chemical properties of tropolone are well documented . Its behavior is intermediate between those of phenol, β-diketones, and benzoic acid: it is readily halogenated and reacts with a diazonium ion like phenol, but does not react readily with most electrophilic reagents used in the Friedel−Crafts, Gattermann, and Kolbe−Schmidt reactions, and it can be regarded as a vinylogous carboxylic acid …”

Section: Introductionmentioning

confidence: 99%

“…Nitrosation of tropolone with sodium nitrite in acetic acid proceeds smoothly, and “5-nitrosotropolone” 1 is obtained in good yield. , This is a key compound that can be derivatized to various 5-substituted tropolones, , such as 5-amino, 5-halo, and 5-carboxyl and further to 5-aryl and 5-heterocyclic substituted compounds. Whether the compound exists as the nitroso structure 1A or its tautomeric oxime structure 1B has long been discussed (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

On the Structure of “5-Nitrosotropolone”

2008

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“…2 Nozoe et al found the reaction of activated troponoids to give 1,2,3-trisubstituted azulenes. 3 Furthermore, Yasunami et al developed a new synthetic method for various azulene derivatives by the reaction of 2H -cyclohepta [b]furan-2-ones with enamines. 4 These methods are highly efficient for the synthesis of azulenes.…”

Section: Introductionmentioning

confidence: 99%

[2 + 2] Cycloaddition reaction of cycloheptatriene with dichloroketene. A novel and efficient synthetic strategy for the synthesis of 2-hydroxyazulene

Yokoyama

Ito

Watanabe

et al. 2001

J. Chem. Soc., Perkin Trans. 1

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The reaction of cycloheptatriene with dichloroketene, generated by the treatment of trichloroacetyl chloride with activated zinc in dry diethyl ether, affords 9,9-dichlorobicyclo[5.2.0]nona-2,4-dien-8-one 2 as a major product together with 3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-2,4-diene-8,2Ј-oxetan)-4Ј-one 3. Structure 3 is elucidated by the X-ray crystallographic analysis of its partially reduced product. Lactone 3 exhibits [1,5] hydrogen-migration in the seven-membered ring to give 3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8,2Ј-oxetan)-4Ј-one 7 without any decarbonylation. The reaction of 2 with diazomethane exhibits ring expansion of the four-membered ring to give 1,1-dichloro-3,3a,4,8a-tetrahydroazulen-2(1H )-one 8. 2-Hydroxyazulene 9 is successfully derived by the reaction of 8 with lithium chloride in good yield. The reaction of 8 with triethylamine exhibits dehydrochlorination to give 3-chloro-8,8a-dihydroazulen-2(1H )-one 10 in high yield. N-(Azulen-2-yl)pyrrolidine is also derived from either 9 or 10 in good yield.

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Cited by 16 publications

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The 2,6-Diisocyanoazulene Motif: Synthesis and Efficient Mono- and Heterobimetallic Complexation with Controlled Orientation of the Azulenic Dipole

The 2,6-Diisocyanoazulene Motif: Synthesis and Efficient Mono- and Heterobimetallic Complexation with Controlled Orientation of the Azulenic Dipole

On the Structure of “5-Nitrosotropolone”

[2 + 2] Cycloaddition reaction of cycloheptatriene with dichloroketene. A novel and efficient synthetic strategy for the synthesis of 2-hydroxyazulene

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