- Isolation of cyclohexadienone intermediates in the photo-fries rearrangement of 2,4-dimethylnaphth-1-yl and 1,4-dimethylnaphth-2-yl 2,4,6-trimethylbenzoates
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Labile cyclohexadienones were isolated for the first time in good yields in the photo-Fries rearrangement of partially blocked naphthyl esters. Upon direct excitation at 313 nm, 1,4-dimethylnaphth-2-yl and 2,4-dimethylnaphth-1-yl 2,4,6-trimethylbenzoates afforded 1-acyl-2-naphthalenone and 2- and 4-acyl-1-naphthalenones, respectively. This isolation is of particular importance as a direct mechanistic proof and also as a convenient route to these thermally less-accessible compounds.
- Mori, Tadashi,Takamoto, Makoto,Saito, Hideaki,Furo, Takahiro,Wada, Takehiko,Inoue, Yoshihisa
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p. 254 - 255
(2007/10/03)
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- Remarkable differences in photo and thermal (acid-catalyzed) reactivities between ortho-and para-acylcyclohexadienones as essential factors determining the overall efficiency of the photo-fries rearrangement
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Successful isolation of ortho and para - acylcyclohexadienones allowed us to comparatively study their ground- and excited-state behavior under a variety of conditions. In neutral solutions, the two isomeric cyclohexdienones showed completely different reactivities for photochemical and thermal reactions, while in acidic methanol both quantitatively afforded the corresponding transesterification product and naphthol. These studies help us understand the detailed photo-Fries rearrangement mechanism, which involves several crucial photochemical and thermal steps.
- Mori, Tadashi,Takamoto, Makoto,Saito, Hideaki,Furo, Takahiro,Wada, Takehiko,Inoue, Yoshihisa
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p. 256 - 257
(2007/10/03)
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- 187. Acid-Catalyzed Cleavage of 1,4-Dimethyl-1,4-dihydronaphthalene 1,4-Endoperoxide. Reactivity of the Resulting Hydroxyperoxy Carbocation with Nucleophiles
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In the presence of acids, 1,4-dimethyl-1,4-dihydronaphthalene 1,4-endoperoxie readily reacts with nucleophiles to produce methyl- and ring-substituted naphthalenes in high yields.The regioselectivity observed depends on the nucleophile.The key intermediate is shown to be the corresponding hydroperoxy carbocation which could be intercepted in certain cases prior to aromatization.The hydroperoxide also undergoes Hock-type cleavage and dimerization giving 2,3-dihydro-1-benzoxepins, 4-methyl-1-naphthol, and 1,2,5,6-tetraoxocane as by-products.
- Jefford, Charles W.,Rossier, Jean-Claud,Kohmoto, Shigeo,Boukouvalas, John
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p. 1804 - 1814
(2007/10/02)
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