- Deacylation-aided C–H alkylative annulation through C–C cleavage of unstrained ketones
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Arene- and heteroarene-fused rings are pervasive in biologically active molecules. Direct annulation between a C–H bond on the aromatic core and a tethered alkyl moiety provides a straightforward approach to access these scaffolds; however, such a strategy is often hampered by the need of special reactive groups and/or less compatible cyclization conditions. It would be synthetically appealing if a common native functional group can be used as a handle to enable a general C–H annulation with diverse aromatic rings. Here, we show a deacylative annulation strategy for preparing a large variety of aromatic-fused rings from linear simple ketone precursors. The reaction starts with homolytic cleavage of the ketone α C–C bond via a pre-aromatic intermediate, followed by a radical-mediated dehydrogenative cyclization. Using widely available ketones as the robust radical precursors, this deconstructive approach allows streamlined assembly of complex polycyclic structures with broad functional group tolerance. [Figure not available: see fulltext.]
- Dong, Guangbin,Xu, Yan,Zhou, Xukai
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p. 703 - 710
(2021/08/09)
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- An Improvement of the Palladium-Catalyzed [4+2] Cycloaddition of o -(Silylmethyl)benzyl Carbonates with Alkenes
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The palladium complex, which is generated in situ from Pd(η 3-C3H5)Cp and tris(4-methoxy-3,5-dimethylphenyl)phosphine, catalyzed the [4+2] cycloaddition of o-(silylmethyl)benzyl carbonates with alkenes. The reaction of the
- Jin, Yushu,Ishizuka, Kentaro,Kuwano, Ryoichi
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supporting information
p. 2488 - 2492
(2015/07/27)
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- Palladium-catalyzed formal [4+2] cycloaddtion of o-xylylenes with olefins
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o-(Silylmethyl)benzylic carbonates reacted with various conjugated olefins in the presence of the palladium catalyst, which was generated in situ from Pd(η3-C3H5)Cp and 1,2-bis(diphenylphosphino)ethane (DPPE). The reaction
- Kuwano, Ryoichi,Shige, Takenori
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p. 3802 - 3803
(2008/02/03)
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- 1,1-, 1,2-, and 1,4-eliminations from the corresponding dihalogenated compounds using Bu3SnSiMe3-F-
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The stannyl anion 2, generated from Me3SiSnBu3(1)6 in the presence of R4NX, CsF or TASF [(Et2N)3SSiMe3F2]7 in DMF under very mild conditions, was used for 1,1-, 1,2-,or 1,4-elimination of an aryl or vinyl halide with an appropriate leaving group at the α-, β-, or δ-position of halogen. Thus, alkylidene carbene 8 is generated from 1,1-dibalo-alkene 6 or 7 and benzyne 10 is generated from 1,2-dibromobenzene 9 and an o-quinodimethane 12 was produced from α,α'-dibromoxylene 11a.
- Sato, Hiroki,Isono, Naohiro,Miyoshi, Irie,Mori, Miwako
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p. 8143 - 8158
(2007/10/03)
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- Utilization of Me3SiSnBu3 in organic synthesis. Generation of o-quinodimethane from α,α'-dibromo-o-xylene and Me3SiSnBu3-CsF
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The reaction of α,α'-dibromo-o-xylene with stannyl anion generated from Me3SiSnBu3 and CsF or TASF [(Et2N)3S+SiMe3F2-] in the presence of dienophiles afforded the [4 + 2] cyclization products in good to moderate yields.
- Sato,Isono,Okamura,Date,Mori
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p. 2035 - 2038
(2007/10/02)
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- The Metal-Ammonia Reduction of Mono- and Dinaphtylbenzenes
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The metal-ammonia reduction of 1- and 2-phenylnaphthalene (9 and 10, respectively), 1,3-bis(1-naphthyl)benzene (5), 1,3-bis(2-naphthyl)benzene (6), 1,4-bis(1-naphthyl)benzene (7), and m-quinquephenyl (8) has been investigated. 9 affords a mixture of isomeric dihydro products together with 1-phenyl-1,2,3,4-tetrahydronaphthalene, and the effect of metal, temperature, and quenching methods on the product distribution is reported. 10 provided only a single dihydro (1,4-)isomer plus a tetrahydro product. both 5 and 7 provided a number of dihydro, tetrahydro, hexahydro, and octahydro products.On the other hand, 6 afforded high yields of a single tetrahydro product with lithium, and exclusively an octahydro product when 5-7 mol of sodium was used.In contrast to the terphenyls, which seem to have a propensity for inner-ring reduction, none of the naphthyl benzenes showed any tendency to reduce in the central benzene ring. m-Quinquephenyl reduced in two rings with no evidence for reduction in the central or outer rings.
- Marcinow, Zbigniew,Rabideau, Peter W.
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p. 3812 - 3816
(2007/10/02)
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- Reduction of Polycyclic Arenes by BH-Boranes, II Borane Catalyzed Hydrogenation of Naphthalenes to Tetralins
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Tetrapropyldiborane(6) (TPDB) and triethylborane (TEB) catalyze the regioselective and partial hydrogenation of naphthalene (N) and a number of substituted naphthalenes at 170 deg C to 200 deg C and hydrogen pressures of 25-100 bar.Tetralin (T) is formed quantitatively.Naphthalene derivatives are mainly hydrogenated in the least substituted ring.In the case of alkyl substituents, Lewis acid catalyzed migration and, to a lesser extent C-C bond rupture, lower the yield of the main tetralin derivative.Chlorinated naphthalenes and at the O-atom derivatized naphthols undergo also partial loss of the chloro or oxygen functional groups.The i nitially added borane acts only as a precatalyst and its slowly converted to catalytically active polyboranes of as yet unknown structures.Keywords: Hydroboranes/ Hydrogenation/ Naphthalenes/ Tetralins
- Yalpani, Mohamed,Lunow, Thomas,Koester, Roland
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p. 687 - 694
(2007/10/02)
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- Chemotherapeutic agents
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A method of treating or preventing viral infections, in particular rhinovirus infections comprising the administration of an effective amount of a 2-phenyltetralin derivative or a heterocyclic analogue thereof. Pharmaceutical compositions containing these compounds, and some novel compounds are also disclosed.
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- STRUCTURE OF THE INTERMEDIATE FORMED IN THE REACTION OF THE STYRENE RADICAL CATION AND NEUTRAL STYRENE.
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The structure of the ion-molecule adduct produced in the gas-phase reaction of the styrene radical cation with neutral styrene has been probed by collisionally stabilizing the adduct and then acquiring its collision-activated decomposition (CAD) spectrum with a tandem mass spectrometer. The CAD spectrum of the adduct is nearly identical with the CAD spectra of the cis- and trans-diphenylcyclobutane radical cations and with the product ion resulting from a 1,4-regiospecific water elimination from the 1,4-diphenylbutan-1-ol radical cation; therefore the radical cations from all four precursors possess the same structure. The DELTA H//f of this radical cation is shown to be less than equivalent to 239 kal/mol; therefore it cannot have the trans-1,2-diphenylcyclobutane structure ( DELTA H//f equals 247 kcal/mol). The results support a two-step mechanism for the left bracket 1 plus 2 right bracket cycloaddition reaction.
- Groenewold,Chess,Gross
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p. 539 - 543
(2007/10/02)
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- Lithium Dialkylamide Induced 1,4-Elimination of Methyl o-Methylbenzyl Ethers: Formation and Reactions of o-Xylylenes
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Lithium dialkylamide induced 1,4-elimination is shown to be a general reaction of methyl o-methylbenzyl ethers, giving o-xylylenes as reactive intermediates.The fate of the intermediates depends on a variety of factors including the base used, the dienophile employed as solvent, or the presence of a suitable located double bond in the substrate.With lithium diisopropylamide (LDA), a significant reaction forms the amine derived from 1,4-addition to o-xylylene.The use of lithium tetramethylpiperidide (LTMP) avoids this addition and allows the study of in situ generated o-xylylene in intermolecular Diels-Alder reactions with simple olefins, where dimerization/polymerization is the major competing pathway.Yields of Diels-Alder adducts range from negligible (cyclohexene) to high (norbornene), with 1-hexene, isoprene, and cyclopentene giving intermediate values.Intramolecular Diels-Alder reactions to form six- and five-membered rings proceed well but are not observed for lower homologue.Second-order rate constants have been obtained for the elimination reaction of some of the substrate ethers, and the effects of structure and temperature on yields of cycloadduct are examined.LTMP is about twice as reactive as LDA in these 1,4-eliminations.
- Tuschka, Theodore,Naito, Katsuyuki,Rickborn, Bruce
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- CATALYTIC ISOMERIZATION OF 1-BENZYLINDANE IN THE PRESENCE OF ALUMINUM CHLORIDE
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The products from enlargement of the polymethylene ring of 1-benzylindane in the presence of aluminum chloride are 1,2,3,4-tetrahydronaphthalene and 2-phenyl-1,2,3,4-tetrahydronaphthalene.By means of labeled atoms it was shown that this rearrangement takes place through the intermediate formation of 2,3,6,7-dibenzobicycloocta-2,6-diene.
- Sakhabutdinov, A. G.,Ageenko, A. A.,Lipovich, V. G.
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p. 1476 - 1479
(2007/10/02)
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