- Transition metal-free regioselective access to 9,10-dihydroanthracenes via the reaction of anthracenes with elemental phosphorus in the KOH/DMSO system
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Anthracene and its 9- or 9,10-substituted (Me, Ph, Cl, Br) derivatives react with red phosphorus (Pn) in the KOH/DMSO superbase system at 85–120 °C to afford 9,10-dihydroanthracenes in good to excellent yields, thus providing simple and clean access to these extensively used dihydroaromatics.
- Kuimov, Vladimir A.,Gusarova, Nina K.,Malysheva, Svetlana F.,Trofimov, Boris A.
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supporting information
p. 4533 - 4536
(2018/11/27)
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- Birch Reduction of Aromatic Compounds by Inorganic Electride [Ca2N]+?e- in an Alcoholic Solvent: An Analogue of Solvated Electrons
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Birch reduction of aromatic systems by solvated electrons in alkali metal-ammonia solutions is widely recognized as a key reaction that functionalizes highly stable π-conjugated organic systems. In spite of recent advances in Birch reduction with regard to reducing agent and reaction conditions, there remains an ongoing challenge to develop a simple and efficient Birch reaction under mild conditions. Here, we demonstrate that the inorganic electride [Ca2N]+?e- promotes the Birch reduction of polycyclic aromatic hydrocarbons (PAHs) and naphthalene under alcoholic solvent in the vicinity of room temperature as a solid-type analogy to solvated electrons in alkali metal ammonia solutions. The anionic electrons from electride [Ca2N]+?e- are transferred to PAHs and naphthalene via alcoholysis in a polar cosolvent medium. It is noteworthy that a high conversion yield to the hydrogenated products is ascribed to the extremely high electron transfer efficiency of 98%. This simple protocol utilizing an inorganic electride offers a direct and practical strategy for the reduction of aromatic compounds and provides an outstanding reducing agent for synthetic chemistry.
- Yoo, Byung Il,Kim, Ye Ji,You, Youngmin,Yang, Jung Woon,Kim, Sung Wng
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supporting information
p. 13847 - 13853
(2018/11/23)
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- Hydrogen-protected acenes
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The first systematic study concerning the hydrogenation of acenes and acene quinones is presented. Phenyl substituted acenes and acene quinones are hydrogenated in excellent yield and with complete regioselectivity using HI-AcOH. The resulting H-protected acenes bear alternating aromatic and non-aromatic rings and are stable, soluble molecules that may be stored indefinitely and then deprotected to afford the parent acenes. In this manner, H-protected acenes have been utilized in the syntheses of several [60]fullerene-acene adducts. Buckminsterfullerene also hydrogenates in HI-AcOH yielding C3v symmetric C60H18. The Royal Society of Chemistry.
- Athans, Andreas J.,Briggs, Jonathan B.,Jia, Wenling,Miller, Glen P.
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p. 2636 - 2641
(2008/09/20)
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- Use of Magnesium Anthracene * 3 THF in Synthesis: Generation of Grignard Compounds and Other Reactions with Organic Halides
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The course (a), (b), (c) (Scheme 1) of the reaction of magnesium anthracene * 3 THF (1) with organic halides (RX) is dependent on the nature of RX.With alkyl halides in THF 1 reacts as a nucleophile, whereby primary as well as secondary alkyl halides produce dialkyldihydroanthracenes (4-4'') and tertiary alkyl halides yield primarily monoalkyl-substituted dihydroanthracenes (2, 2').With bromo- and iodobenzene in THF 1 reacts predominantly as a radical with H atom abstraction from the solvent affording benzene and 9.The formation of Grignard compounds (5) and anthracene (6), originating from primary and secondary alkyl and aryl halides and 1 in toluene or ether at elevated temperatures, is not caused by the reaction of 1 but by the "active magnesium" (Mg*) formed by decomposition of 1 in these solvents.In contrast, allyl, propargyl, and benzyl halides react with 1 independently of the solvent under mild conditions to produce 5 and 6.Allyl- and the difficultly accessible allenylmagnesium chloride can be prepared in THF at -78 and 0 deg C, respectively, from the corresponding halides and ordinary Mg powder via catalytic amounts of 1.
- Bogdanovic, Borislav,Janke, Nikolaus,Kinzelmann, Hans-Georg
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p. 1507 - 1515
(2007/10/02)
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- Magnesium Adducts of Substituted Anthracenes - Preparation and Properties
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2-Methyl-, 1,4-dimethyl-, 9-methyl-, 9-ethyl-, 9,10-dimethyl-, and 9-phenylanthracene (1a-f) react with magnesium in THF at room temperature to afford the corresponding substituted magnesium anthracenes 2a-f. 9,10-Diphenylanthracene (1g), however, reacts with magnesium under the same conditions to produce the deep-blue magnesium bis(9,10-diphenylanthracenide) * 6 THF (4g).Upon heating to 60 deg C in THF, 4g reversibly dissociates to give magnesium 9,10-diphenylanthracene * 3 THF (2g) and 1g, while prolonged heating at 60 deg C causes decomposition of 2g to active magnesium (Mg*) and 1g.In THF 2a-c, e, and f exhibit temperature-dependent equilibria with 1a-c, e, and f and magnesium.Compared with magnesium anthracene * 3 THF (2), these equilibria are strongly shifted toward substituted anthracenes and magnesium, and only at 0 deg C high conversions are achieved.The magnesium exchange between 2 and the substituted anthracenes 1a, b, and f in THF has been experimentally verified. 2a, e, and f react with organic halides in the same way as 2, however, in the case of allyl, propargyl, and benzyl chloride the yields of Grignard compounds are lower than for 2; with bromobenzene, the tendency for the radical transfer reaction is stronger than for 2.Magnesium 9,10-dimethylanthracene (2e) reacts with ethyl acetate to give the bicyclic tertiary alcohol 9 by an intramolecular C-C coupling reaction.
- Bogdanovic, Borislav,Janke, Nikolaus,Kinzelmann, Hans-Georg,Seevogel, Klaus,Treber, Joachim
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p. 1529 - 1535
(2007/10/02)
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- Hydrogen Transfer between Anthracene Structures
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This work reports results of kinetic studies of hydrogen migration between 9,10-dihydro positions in anthracene structures.The transfer of two H atoms from 9,10-dimethyl-9,10-dihydroanthracene (AnH2) to 2-ethylanthracene (EAn) follows simple bimolecular kinetics with k/M-1 s-1=109.64+/-0.14exp (250-375 deg C) At 300-350 deg C, H transfer to 9,10-dimethylanthracene led to nearly equimolar mixtures of cis- and trans-9,10-dihydroanthracene, consistent with a free radical mechanism.The rate-limiting step appears to be transfer of a single benzylic H atom from a donor molecule to an acceptor molecule, resulting in the formation of two highly stabilized free radicals.Reactions of this nature are likely to serve as major sources of free radicals in condensed-phase thermolysis reactions.Measurements of their rate constants offer a new, relatively direct means of determining bond strengths.From the above rate expression, we derive an AnH-H bond strength of 78.4+/- 1.8 kcal mol-1.From literature data for a similar reaction (Halpern et al.) we obtain an H-Mn(CO)5 bond strength of 63 kcal mol-1.Based on an observed lowering of the reaction rate with added anthracene, a rate constant was derived for β-H transfer from a2-ethyl-9-hydroanthryl radical to anthracene.At 350 deg C, this value was 120 M-1 s-1, indicating a high activation barrier (ca. 18 kcal mol-1) for this seldom reported process.
- Billmers, R.,Griffith, L. L.,Stein, S. E.
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p. 517 - 524
(2007/10/02)
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- Alternative Routes for Reductive Alkylations in Liquid Ammonia and Their Selection via Spectroscopic Evidence
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A wide range of unsaturated hydrocarbons have been reduced with alkali metals in liquid ammonia and the carbanionic intermediates detected in situ by NMR and ESR spectroscopy.The substrates cluster into three different groups depending on whether they (i) persist as dianions, (ii) are protonated by ammonia to afford monohydro anions, or (iii) undergo further electron transfer/protonation steps to yield polyhydro derivatives.The alternative modes of behavior can be correctly predicted on the basis of the relevant atom localization energies.The spectroscopic findings are extremely helpful in rationalizing the results of reductive alkylation experiments and in controlling the regioselectivity of novel quenching reactions.
- Muellen, Klaus,Huber, Walter,Neumann, Gerd,Schnieders, Christoph,Unterberg, Heinz
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p. 801 - 807
(2007/10/02)
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