Reactions of acylaminoquinone tosylhydrazones. 4. A new synthesis of pyrrolo[1,2-a]indoloquinone and related compounds via benzoxazoline by thermolysis and photolysis

Akiba, Mitsuo; Kosugi, Yoshiyuki; Takada, T.

doi:10.1021/jo00417a017

Cited by 18 publications

(11 citation statements)

References 2 publications

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“…Intramolecular γ-hydrogen abstraction by the quinone 284 would produce a diradical which can rearrange via spiroaziridine 285 to an unstable, yet isolable, oxazoline 287 . [268] The oxazoline 287 then rearranges to compound 288 , bearing the characteristic skeleton of the mitomycins. It was proposed that in polar solvents, zwitterionic intermediate 286 would be favored and that it could undergo intramolecular nucleophilic attack to give ring-closed quinones, arriving at final product 288 .…”

Section: The Mitomycins: Synthetic Studiesmentioning

confidence: 99%

Mitomycinoid Alkaloids: Mechanism of Action, Biosynthesis, Total Syntheses, and Synthetic Approaches

et al. 2013

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Section: The Mitomycins: Synthetic Studiesmentioning

confidence: 99%

Mitomycinoid Alkaloids: Mechanism of Action, Biosynthesis, Total Syntheses, and Synthetic Approaches

et al. 2013

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“…[8] However, to the best of our knowledge, the nonstabilized diazo compounds generated in situ from N-tosylhydrazones have only been sporadically studied for intramolecular aromatic substitution and Büchner reactions. [9] As a continuation of our own interest in this area, herein we report transition-metal-free reactions of the N-tosylhydrazones as shown in Scheme 2. Depending on the substrates, the reaction either undergoes intramolecular aromatic substitution or intramolecular Büchner reaction.…”

mentioning

confidence: 92%

Transition‐Metal‐Free Intramolecular Carbene Aromatic Substitution/Büchner Reaction: Synthesis of Fluorenes and [6,5,7]Benzo‐fused Rings

et al. 2015

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Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by Rh II catalysts with a-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.

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“…15 It was shown, by laser flash photolysis, that the photocyclization of the phenyl-and 4-anisyl-p-benzoquinones in dibenzofuran 16,17 involves the triplet state of the quinone and an hypothetical cyclized transient species, X, which, depending on the solvent, rearranges to the photoproduct or reverts to the starting quinone. However, this mechanism is certainly not valid for all of the substituted p-benzoquinones yielding a benzofuran moiety upon photocyclization.…”

Section: Introductionmentioning

confidence: 99%

Photophysics and Photochemistry of a Lignin-like Quinoid Dimer, 4,4‘-Dimethoxybiphenyl-2,5,2‘,5‘-bisquinone, in Relation to Color Alteration of Woody Materials Exposed to Daylight

1999

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4,4′-Dimethoxybiphenyl-2,5,2′,5′-bisquinone 1 is thought to be issued, in wood and lignin-rich pulps, from the photochemical coupling and oxidation of methoxy(hydro)quinone. Under irradiation in solution, 1 is transformed to a highly colored dibenzofuran derivative, 2, as unique photoproduct. The mechanism of the conversion 1 f 2 has been studied by laser flash photolysis and by quantum yield measurements in several solvents at various temperatures. The reaction proceeds via the triplet state of 1 and a cyclized X transient species which rearranges to 2 by a sequence of deprotonation-protonation reactions, quite efficiently in polar or acidified solutions but with a low yield in nonpolar solvents. As temperature increases, the quantum yield increases in polar solutions but decreases in nonpolar solvents. This unusual temperature dependence is explained by activation energy barriers on the cyclization 3 1* f X and reopening X f 1 elementary reactions, ≈ 35.5 and 58.5 kJ/mol respectively, and by a conversion X f 2 much faster in polar solvents than in nonpolar ones. The zwitterionic or biradicaloid structure of X is discussed on the basis of semiempirical calculations (AM1 or PM3) and of spectroscopic and kinetic measurements. Under laser flash photolysis conditions, a special mechanism involving a second-order rearrangement of X was found to be very efficient in any type of solvents.

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Reactions of acylaminoquinone tosylhydrazones. 4. A new synthesis of pyrrolo[1,2-a]indoloquinone and related compounds via benzoxazoline by thermolysis and photolysis

Cited by 18 publications

References 2 publications

Mitomycinoid Alkaloids: Mechanism of Action, Biosynthesis, Total Syntheses, and Synthetic Approaches

Mitomycinoid Alkaloids: Mechanism of Action, Biosynthesis, Total Syntheses, and Synthetic Approaches

Transition‐Metal‐Free Intramolecular Carbene Aromatic Substitution/Büchner Reaction: Synthesis of Fluorenes and [6,5,7]Benzo‐fused Rings

Photophysics and Photochemistry of a Lignin-like Quinoid Dimer, 4,4‘-Dimethoxybiphenyl-2,5,2‘,5‘-bisquinone, in Relation to Color Alteration of Woody Materials Exposed to Daylight

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