- Preparation method of 10,10-dimethylanthrone
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The invention belongs to the field of drug synthesis and provides a novel method of synthesizing melitracen hydrochloride intermediate 10,10-dimethylanthrone. The 10,10-dimethylanthrone is prepared from phthalic anhydride as a start material through two-step Grignard reaction and three-step closed-ring reaction. The total yield is up to 30%, and the purity of the finished intermediate is higher than 98.0%. Compared with traditional synthetic processes, the novel process herein has simple steps and greatly reduced production cost, causes little environmental pollution and helps greatly solve the environmental issue caused by the production of 10,10-dimethylanthrone.
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Paragraph 0021; 0023; 0024; 0028; 0029; 0032
(2019/06/30)
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- The effect of pressure on hydrogen transfer reactions with quinones
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The effect of pressure on the oxidation of hydroarenes 3-9 with 2,3-dichloro-5,6-dicyano-1,4-quinone (DDQ; 1a) or o-chloranil (10), leading to the corresponding arenes, has been investigated. The activation volumes were determined from the pressure dependence of the rate constants of these reactions monitored by on-line UV/Vis spectroscopic measurements in an optical high-pressure cell (up to 3500 bar). The finding that they are highly negative and only moderately dependent on the solvent polarity (ΔV ?=-13 to -25 in MTBE and -15 to -29 cm3mol -1 in MeCN/AcOEt, 1:1) rules out the formation of ionic species in the rate-determining step and is good evidence for a hydrogen atom transfer mechanism leading to a pair of radicals in the rate-determining step, as was also suggested by kinetic measurements, studies of kinetic isotope effects, and spin-trapping experiments. The strong pressure dependence of the kinetic deuterium isotope effect for the reaction of 9,10-dihydroanthracene 5/5-9,9,10,10-D4 with DDQ (1a) can be attributed to a tunneling component in the hydrogen transfer. In the case of formal 1,3-dienes and enes possessing two vicinal C-H bonds, which have to be cleaved during the dehydrogenation, a pericyclic hydrogen transfer has to considered as one mechanistic alternative. The comparison of the kinetic deuterium isotope effects determined for the oxidation of tetralin 9/9-1,1,4,4-D4/9-2,2,3,3-D4/9-D 12 either with DDQ (1a) or with thymoquinone 1c indicates that the reaction with DDQ (1a) proceeds in a stepwise manner through hydrogen atom transfer, analogously to the oxidations of 1,4-dihydroarenes, whereas the reaction with thymoquinone 1c is concerted, following the course of a pericyclic hydrogen transfer. The difference in the mechanistic courses of these two reactions may be explained by the effect of the CN and Cl substituents in 1a, which stabilize a radical intermediate better than the alkyl groups in 1c. The mechanistic conclusions are substantiated by DFT calculations.
- Wurche, Frank,Sicking, Wilhelm,Sustmann, Reiner,Klaerner, Frank-Gerrit,Ruechard, Christoph
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p. 2707 - 2721
(2007/10/03)
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- Regioselective alkylation of anthrone, 5,5-dimethyl-3-isoxazolidinone and 4-methylquinolone by phase transfer catalysis
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Anthrone (1) can be alkylated selectively to give O-, C,O- or C,C-substituted compounds 2, 4, or 5, respectively. Similarly, 5,5-dimethyl-3-isoxazolidinone (6) and 4-methylquinolone (9) yield N- or O-derivatives 7 and 8 or 10 and 11, respectively. The product ratios can be influenced strongly sometimes by use of different phase transfer catalysts, but the sensitivity of each reaction towards the catalysts is unique.
- Dehmlow, Eckehard Volker,Bollhoefer, Joerg,Thye, Gorden
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p. 113 - 115
(2007/10/03)
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- Thermolabile Hydrocarbons, 34. - Thermal Stability of 9,9'-Bixanthene and 9,9',10,10'-Tetrahydro-10,10,10',10'-tetramethyl-9,9'-bianthracene. - Stabilisation Energies of Planar Benzhydryl Radicals
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The thermal cleavage of the central CC bonds in the title compounds was investigated.The activation parameters were obtained from kinetics and the equilibrium enthalpies and entropies from the temperature dependence of the equilibrium radical concentrations, determined by quantitative ESR. ΔH(excit.) and ΔHDiss are nearly identical but not ΔS(excit.) and ΔSDiss, as expected.The radical stabilisation enthalpies RSE obtained from these data (RSE: 7a = 17.9+/-1.3; 7b = 15.6+/-1.4 kcal/mol) correspond closely to twice the RSE of α-phenylethyl radicals (8.0+/-1.5 kcal/mol) determined previously.The smaller RSE of the benzhydryl radical (12.9+/-0.9 kcal/mol), therefore, must be due to its nonplanarity. - Key Words: C-C Bond cleavage, energetics and kinetics of / Radicals, stability of / ESR
- Herberg, Clemens,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 2065 - 2072
(2007/10/02)
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- Free energy and entropy changes in vertical and nonvertical triplet energy transfer processes between rigid and nonrigid molecules. A laser photolysis study
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The free energy and entropy changes associated with intermolecular triplet energy transfer (TT) processes were determined by direct measurement of the equilibrium constant using a laser flash photolysis technique. 10,10-Dimethylanthrone and 9,9-dimethylfluorene were synthesized and used as a "rigid" donor and acceptor, respectively, in comparison with 4-methylbenzophenone, a "nonrigid" donor, and 4-methylbiphenyl, a "nonrigid" acceptor, in the TT reactions. Both the nonrigid donor and the nonrigid acceptor lose entropy while going from the twisted ground state to the planar triplet state. The ΔS values for 4-methylbenzophenone and 4-methylbiphenyl are 0.5-1.0 and 2.5-3.0 gibbs/mol, respectively.
- Zhang, Daisy,Closs, Gerhard L.,Chung, Dutch D.,Norris, James R.
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p. 3670 - 3673
(2007/10/02)
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- A Convenient Synthesis of 9,9-Dialkyl-9,10-dihydroanthracenes and 10,10-Dialkylanthrones: Silicon-Mediated Regioselective Dialkylation of 9,10-Dihydroanthracene
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Described is a short and convenient approach to the synthesis of 9,9-dialkyl-9,10-dihydroanthracenes, 9,9,10-trialkyl-9,10-dihydroanthracenes, and 10,10-dialkylanthrones, some of which are otherwise unknown or inaccessible by conventional methods.Deprotonation of 9-(trimethylsilyl)-9,10-dihydroanthracene (2; 9-(trimethylsilyl)-9,10-DHA) followed by reaction with alkyl halides (RX) produces 9-alkyl-9-(trimethylsilyl)-9,10-DHAs 3-7 in 80-90percent yields.Treatment of 3-7 with n-BuLi produces the 10-lithio derivatives that rearrange to 9-alkyl-9-lithio-10-(trimethylsilyl) intermediates; subsequent alkylation with RX generates 9,9-dialkyl-10-(trimethylsilyl)-9,10-DHAs 8-19.Formation of single stereoisomers 13-19 was suggested by NMR and confirmed in two cases, 15 and 16, by X-ray structure determination.The trimethylsilyl group is removed by tetrabutylammonium fluoride (TBAF) to provide 9,9-dialkyl-9,10-DHAs 20-29 with impressive yields.Oxidation of either the 9,9-dialkyl-9,10-DHAs or 9,9-dialkyl-10-(trimethylsilyl)-9,10-DHAs with Cr(VI) oxidant furnished 10,10-dialkylanthrones 36-41 in 80-90percent yields.
- Dhar, Raj K.,Clawson, D. K.,Fronczek, Frank R.,Rabideau, Peter W.
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p. 2917 - 2921
(2007/10/02)
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- Ketene. Part 23. Conformational Control of the Addition Reactions of Ketenes with N-Phenylnitrones
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X-Ray analysis shows that the nitrone group in (5a) is not distorted, disproving a previous explanation for the formation of oxazolidinones rather than indolones in the reactions with ketenes.Nitrone (5c) reacts with dimethylketene and diphenylketene to form oxazolidinones (6c,d) whereas nitrones (5d) and (5e) under similar conditions form indolone derivatives (9).Oxazolidinone formation by the reaction of ketenes with nitrones (5a-c) results from restricted rotation about the N-phenyl bond preventing the -migration (3) -> (4), which precedes indolone formation.
- Falshaw, Christopher P.,Hashi, Nur A.,Taylor, Giles A.
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p. 1837 - 1844
(2007/10/02)
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- REARRANGEMENT AND FRAGMENTATION REACTIONS OF BLOCKED AROMATIC ALCOHOLS.
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A report is presented on the products obtained from reaction of alcohol and its secondary analogue with acidic solutions. It is found that in solutions containing acetic anhydride both give solely products resulting from molecular rearrangements. Factors responsible for determining the reaction products and reactivities of the starting alcohols are discussed.
- Bhattacharya,Miller
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p. 3242 - 3247
(2007/10/02)
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- DIHYDROSILAANTHRACENYLIDENE AND DIHYDROANTHRACENYLIDENE
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Carbenes generated from 10-diazo-9,9-dimethyl-9,10-dihydro-9-silaanthracene and 10-diazo-9,9-dimethyl-9,10-dihydroanthracene gave hydrogen abstraction products by the triplet nature of these carbenes.The triplet dihyrosilaanthracenylidene was shown by the electron spin resonance study.
- Sekiguchi, Akira,Ando, Wataru,Sugawara, Tadashi,Iwamura, Hiizu,Liu, Michael T. H.
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p. 4095 - 4098
(2007/10/02)
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- Polycyclen vom Triangulen-Typ, II. Dreifach ortho-verbrueckte Triphenylmethan-Derivate
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The syntheses of the new polycyclic systems 12,12c-dihydro-4,4,8,8,12,12-hexamethyl-4H,8H-dibenzopyrene (8), 11,11c-dihydro-7,7,11,11-tetramethyl-7H-naphthaceanthrylene (43), and 9,13b-dihydro-5,5,9,9-tetramethyl-1,13-ethano-5H-naphthanthracene (44) are reported.The spectroscopic data are in accordance with a pyramidal C3v-structure for 8, a similar Cs-structure for 43, and a flexible, helical C1-structure for 44.Furthermore, 8 can be transformed into its rapidly inverting pyramidal anion 11 and into its cation 9 which most probably is planar.
- Hellwinkel, Dieter,Aulmich, Gerhard,Melan, Michael
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