- Reduction method of electronic salt reaction liquid and unsaturated aromatic hydrocarbon compound
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To the reduction method, tetrahydrofuran is used as a solvent and an electron trapping agent, metal lithium is used as a reducing agent, tertiary butanol is used as a reducing agent, and the unsaturated aromatic hydrocarbon compound is reduced under -10 - 0 °C conditions. The raw material tetrahydrofuran is used in the invention. Metal lithium and tert-butyl alcohol are all conventional chemical products, and are simple and easy to obtain. After the reaction is finished, excess lithium and solvent are recovered, and directly used to realize low cost, low pollution and high yield.
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Paragraph 0080-0083
(2021/11/10)
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- Rhodium(I)-Catalyzed Enantioselective C(sp3)—H Functionalization via Carbene-Induced Asymmetric Intermolecular C—H Insertion?
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Transition-metal-catalyzed C—H insertion of metal-carbene represents an excellent and powerful approach for C—H functionalization. However, despite remarkable advances in metal-carbene chemistry, transition metal catalysts that are capable of enantioselective intermolecular carbene C—H insertion are mainly constrained to dirhodium(II) and iridium(III)-based complexes. Herein, we disclose a new version of asymmetric carbene C—H insertion reaction with rhodium(I) catalyst. A highly enantioselective rhodium(I) complex-catalyzed C(sp3)—H functionalization of 1,4-cyclohexadienes with α-aryl-α-diazoacetates was successfully developed. By using chiral bicyclo[2.2.2]-octadiene as ligand, rhodium(I)-carbene-induced asymmetric intermolecular C—H insertion proceeds smoothly at room temperature, allowing access to a diverse variety of α-aryl-α-cyclohexadienyl acetates and gem-diaryl-containing acetates in good yields with good to excellent enantioselectivities (up to 99% ee). Furthermore, the synthetic utility of the reaction was highlighted by facile synthesis of a novel cannabinoid CB1 receptor ligand. This method may offer a new opportunity for the development of therapeutically exploitable cannabinoid receptor type ligands in medicinal chemistry.
- Liu, Bo,Xu, Ming-Hua
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supporting information
p. 1911 - 1915
(2021/05/31)
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- Comparison of the singlet oxygen ene reactions of cyclic versus acyclic β,γ-unsaturated ketones: An experimental and computational study Dedicated to Professor Waldemar Adam on the occasion of his 75th birthday
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The photooxygenation of two β,γ-unsaturated ketones was studied by experimental and computational methods: 5-methyl-hex-4-en-2-one (1) and cyclohex-3-en-1-one (6) as model compounds for acyclic versus cyclic deconjugated enones. The open-chain substrate delivered a 1:1 mixture of regioisomers 2a,b following the established cis-selectivity model whereas the cyclic substrate reacts with 1O2 to give preferentially the conjugated product 7. This effect is in agreement with the mechanistic two-stage no-intermediate model and on a computational level corresponds to a regioselectivity control following the steepest decent pathway from the corresponding transition stages in a valley ridge potential energy surface region.
- Griesbeck, Axel G.,Goldfuss, Bernd,Leven, Matthias,De Kiff, Alan
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supporting information
p. 2938 - 2941
(2013/06/27)
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- Temporary thio-derivatization in the synthesis of (+)-4-acetylbromoxone
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A stereocontrolled synthesis of the marine natural products (+)-bromoxone (1) and (+)-4-acetylbromoxone (2) is reported. The sequence features the enzymatic kinetic resolution of 4-hydroxycyclohexenone (6) via its S-benzyl adduct. Thereafter, a base-mediated elimination-silylation generated an optically active (-)-4S-4-tert-butyldimethylsilyoxycyclohexenone (5), which then underwent diastereoselective epoxidation. Saegusa-Ito oxidation enabled formation of the corresponding α,β-unsaturated ketone 13. Bromination-elimination and subsequent removal of the silicon protecting group afforded (+)-bromoxone (1) which was converted into (+)-(4S,5R,6R)-4-acetoxy-2- bromo-5,6-epoxycyclohex-2-enone (2) [(+)-4-acetylbromoxone]. Using a luciferase gene reporter assay ED50 for NFκB inhibition of 9 μM was determined.
- O'Byrne, Aisling,O'Reilly, Steven,Tighe, Catherine,Evans, Paul,Ciuffini, Laura,Gabriella Santoro
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p. 5936 - 5938
(2013/01/13)
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- The thio-adduct facilitated, enzymatic kinetic resolution of 4-hydroxycyclopentenone and 4-hydroxycyclohexenone
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The addition of 3,4-dimethoxybenzyl thiol 8, as a benzyl thiol surrogate, to racemic 4-hydroxycyclopent-2-enone 2 and 4-hydroxycyclohex-2-enone 15 gave the corresponding cis-adducts (±)-3-(3,4-dimethoxybenzylthio)-4- hydroxycyclopentanone 4b and (±)-3-(3,4-dimethoxybenzylthio)-4- hydroxycyclohexanone 16 with good diastereocontrol. In both cases, subsequent treatment with vinyl acetate, in the presence of a lipase enabled enantiomer resolution. Thus, (+)-16 and the acetate of its enantiomer, (-)-(1R,2S)-2-(3,4- dimethoxybenzylthio)-4-oxocyclohexyl acetate, (-)-17 were isolated in 98% enantiomeric excess. Based on the 1,4-dioxygenation pattern, (-)-17 can be used to prepare both enantiomers of 4-(tert-butyldimethylsilyloxy)cyclohex-2-enone 19. Firstly, saponification, with a sub-stoichiometric amount of NaOMe, followed by a one-pot silyl ether formation-sulfide elimination sequence gave (+)-19. Then using the same starting material a 6-step sequence, featuring a diastereoselective NaBH4 reduction and a Cope-type sulfoxide elimination, gave (-)-19.
- O'Byrne, Aisling,Murray, Cian,Keegan, Dearbhla,Palacio, Carole,Evans, Paul,Morgan, Ben S.
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supporting information; experimental part
p. 539 - 545
(2010/05/11)
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- Stereoselective total synthesis of (+)-varitriol
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Stereoselective total synthesis of (+)-varitriol, an antitumor natural product, was accomplished by two versatile strategies starting from the commercially available d-(-)-ribose and ethyl (S)-lactate. The key steps involved in the synthesis of the target molecule are epoxidation, cyclization, dihydroxylation and Diels-Alder reaction.
- Srinivas,Sridhar,Rao, K. Rama
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body text
p. 8527 - 8535
(2010/11/18)
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- Ammonia-free Birch reductions with sodium stabilized in silica gel, Na-SG(I)
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Ammonia-free Birch reduction conditions were developed based upon sodium stabilized in silica gel for a variety of substrates. In general, the yields were similar to those reported for lump sodium in liquid ammonia.
- Costanzo, Michael J.,Patel, Mitul N.,Petersen, Kathryn A.,Vogt, Paul F.
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supporting information; experimental part
p. 5463 - 5466
(2010/01/11)
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- Preparation of 1-Alkoxy-1,3-cyclohexadienes via Iron Complexation/Decomplexation
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A synthetic method for the preparation of 1-alkoxy-1,3-cyclohexadienes is presented. Iron complexation/decomplexation is used to produce and purify the desired compound without contamination of isomeric by products.
- Rennels, Roger A.,McClusky, John V.
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p. 651 - 656
(2007/10/03)
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- Reductions with lithium in low molecular weight amines and ethylenediamine
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Reductions of several types of compounds with lithium and ethylenediamine using low molecular weight amines as solvent are described. In all cases 1 mol of ethylenediamine or N,N'-dimethylethylenediamine per gram-atom of lithium was used. In some cases it was beneficial to add an alcohol as a proton donor. These reaction conditions were applied to the debenzylation of N-benzylamide and lactams which are refractory to hydrogenolysis with hydrogen and a catalyst. N-Benzylpilolactam 2, synthesized from pilocarpine hydrochloride in refluxing benzylamine, was debenzylated in good yield using 10 gram-atoms of lithium per mole (10 Li/mol) of 2 in n-propylamine. The debenzylation of N-benzyl-N-methyldecanoic acid amide, 4 (6 Li/mol), in t-butylamine/N,N'-dimethylethylenediamine gave N-methyldecanoic acid amide 6 in 70% yield. Alternatively, reduction of 4 (7 Li/mol) in t-butanol/n-propylamine/ethylenediamine gave n-decanal 12 in 36% yield. Using the same conditions, thioanisole, 1-adamantane-p-toluenesulfonamide, and 1-adamantane methyl p-toluenesulfonate were reduced with 3, 7, and 7.2 Li/mol of compound to give thiophenol (74%), adamantamine (91%), and 1-adamantane methanol (75%), respectively. In this solvent system naphthalene and 3-methyl-2-cyclohexene-1-one were reduced to isotetralin (74%) and 3-methyl cyclohexanone (quantitative) with 5 and 2.2 Li/mol of starting compound, respectively. Oximes and O-methyloximes were reduced to their corresponding amines using 5 and 8 Li/mol of compound, respectively. Anisole was also reduced to 1-methoxy-1,4-cyclohexadiene with 2.5 Li/mol of anisole. Undecanenitrile was reduced to undecylamine with 8.6 Li/mol. Additionally, a base-catalyzed formation of imidazolines from a nitrile and ethylenediamine was also explored.
- Garst,Dolby,Esfandiari,Fedoruk,Chamberlain,Avey
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p. 7098 - 7104
(2007/10/03)
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- Synthesis based on cyclohexadienes: Part 101 synthesis of 5,5'-dimethyl-7-methoxy-4-oxatricyclo[4.3.1.03,7]decan-2-ones
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Synthesis of 5,5-dimethyl-7-methoxy-4-oxatricyclo[4,3,1,03,7]-decan-2-one 3a, a novel heterocyclic ring system present in morellin 1, and its 3-substituted derivatives 3b-e, is described from the Diels-Alder adducts 7, available from 1-methoxycyclohexa-1,4-dienes 4. Two routes, which involved the halocyclisation and the oxidative addition, were investigated for the conversion of the adducts 7 into 3. While the halocyclisation method resulted in mixtures, excellent yields of the target molecule were obtained by the second method. Solvolysis of the bromoether 9 resulted in a mixture of rearrangement products 10, 13, 15 and 16.
- Raghavan,Subba Rao
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p. 2599 - 2616
(2007/10/02)
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- The regioselectivity of the Birch reduction
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The reaction mechanism of the Birch reduction was investigated with a view of determinig how the regioselectivity is controlled. Regioselectivity is determined in the first step of radical anion protonation and in the second step of cyclohexadienyl carbanion protonation. It was ascertained that the rate-determining step of the Birch reduction of anisole was radical anion protonation, consistent with the observation of Krapcho and Bothner-By in the case of benzene reduction. A new approach to determining the regioselectivity of the two steps of the Birch reduction was devised. This was predicated on an enhanced primary deuterium isotope effect anticipated for radical anion protonation relative to that expected for cyclohexadienyl carbanion protonation. The approach utilized a partially deuterated medium. The method was applied to the reductions of anisole, 1,3-dimethoxybenzene, 3-methoxytoluane, and 2-methoxynaphthalene. The basic assumption of greater selectivity of the radical anion of the first step relative to the carbanion of the second step was explored in the cases of benzene and anisole and confirmed. In the examples studied, ortho protonation of the radical anion was found to predominate. With a view of understanding the regioselectivity of the two steps, quantum mechanical computations were carried out on several facets of the reaction. Electron density distributions of the radical anions were determined as well as the energies of radical products of some radical anion protonations. Similarly, the energies were obtained for the partially protonated radical anion species at several points along the reaction coordinate. In addition, electron densities were obtained for cyclohexadienyl anion. Theory was then correlated with experiment.
- Zimmerman, Howard E.,Wang, Patricia A.
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p. 2205 - 2216
(2007/10/02)
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- Synthesis of (±) cyclohexane-1(R), 2(R), 4(R)-triol-triphosphate, a deoxygenated analog of myo-inositol-1,4,5-triphosphate
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For the use in the studies of inositol-phosphates, (±) cyclohexane-1(R), 2(R), 4(R)-triol-triphosphate 2 was synthesized from anisole. The synthesis used 1,2-benzenedimethanol as a ketone and phosphate protective group which induced easy crystallization of the intermediates. Regeneration of the free ketone 9 under mild conditions followed by its selective reduction and phosphorylation by the phosphite method gave the expected compound 2.
- Schmitt,Spiess,Schlewer
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p. 2013 - 2016
(2007/10/02)
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- Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Carbohexa-1,4-dienes
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10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2.The product mixture compositions are determined through capillary GLC.On storage at +6 deg C some rearomatization of the 1,4-cyclohexadienes 2 occurs.Data of the 1H- and 13C-.n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given.For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized.Acid-catalyzed addition of alcohols to the 1,4-cyclohexadienes systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30percent.Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
- Beger, J.,Thomas, B.,Vogel, T.,Kirmse, K.,Lang, R.
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p. 481 - 488
(2007/10/02)
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- Through Space Interactions of Double Bonds by Photoelectron Spectroscopy
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Steric effects between double bonds and remote polar substituents, previously manifested in nuclear magnetic resonance (NMR) spectra, are also evident in the ultraviolet photoelectron spectra (USP).An ether functionality was introduced at the 3-axial position of exo-methylenecyclohexane by means of acetal groups ( dimethyl and ethylene).The 3-axial ether group destabilizes the ? orbital on the double bond by 0.1-0.2 eV by a through space interaction (the 3-equatorial ether group by itself has little or no effect).This interaction apparently is responsible for the decreased proportion of 3-axial methoxyl observed by NMR spectroscopy.In contrast, 4-axial ether functionalities in cyclohexene show a slight stabilizing of the ? orbital by through bond electron withdrawal.These results also agree with the NMR observations, since the endocyclic double bond of cyclohexene permits a much larger proportion of 4-axial methoxyl.Ab initio calculations support the observations by paralleling the observed ?-orbital energies and by providing electron densities.Whereas 3-axial methoxyl clearly polarizes the double bond in methylenecyclohexane, 4-axial methoxyl has little or no effect on the electron densities of cyclohexene, even though methoxyl is closer to the endocyclic than to the exocyclic double bond.The NMR, UPS, and ab initio results provide an initial understanding of the three dimensionality of the ?-electron steric effects.
- Lambert, Joseph B.,Xue, Liang,Bosch, Richard J.,Taba, Kalulu M.,Marko, Dale E.,et al.
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p. 7575 - 7579
(2007/10/02)
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- Thermodynamics of Vinyl Ethers. 31. Isomer Equilibria in Some Six- and Seven-Membered Cyclic Dienes
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The relative thermodynamic stabilities of 1,3-cyclohexadiene and 1,4-cyclohexadiene, together with a number of their alkoxy and other derivatives and some related seven-membered cyclic dienes, have been determined by chemical equilibration in Me2SO and cyclohexane solution at various temperatures.The values of the thermodynamic parameters ΣG, ΔH, and ΔS for the isomerization processes involved are discussed and show clearly that the apparently conjugated diene system of 1,3-cyclohexadiene is devoid of conjugation, contrary to that of 1,3-cycloheptadiene.
- Taskinen, Esko,Nummelin, Kari
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p. 4844 - 4847
(2007/10/02)
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- A SAFE AND CONVENIENT NEW PROCEDURE FOR REDUCING AROMATIC COMPOUNDS TO BIRCH-TYPE PRODUCTS
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Aromatic compounds can be reduced by a calcium-amine-t-butyl alcohol system to products which are identical to those obtained by a Birch reduction of the same substrates.
- Benkeser, Robert A.,Laugal, James A.,Rappa, Angela
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p. 2089 - 2092
(2007/10/02)
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- Birch Reductions of Methoxyaromatics in Aqueous Solution
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A Birch-like electroreduction of methoxyaromatics in aqueous solutions was achieved, probably through the intermediacy of a tetrabutylammonium amalgam.
- Swenson, Karl E.,Zemach, Dvora,Nanjundiah, Chenniah,Kariv-Miller, Essie
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p. 1777 - 1779
(2007/10/02)
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- Organophosphorus Redox Systems
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Redox systems involving R2P-, R2P(X)-, and R3P+ -substituted benzenes and biphenyls have been studied by cyclic voltammetry in dimethylformamide.The first one-electron reduction was found to be reversible in several instances, and stable radical anions, cations and uncharged radicals were detected by high-resolution electron spin resonance.The second reduction step was found to be irreversible in all cases investigated.The electrochemical and spectroscopic data illustrate the considerable difference in acceptor strength between R2P and R3P+ substituents; MO calculations of the radical species give a quantitative measure for this difference and for the overall substituent effects.A comparison is made between the organophosphorus redox systems presentented and the quinone/hydroquinone redox systems.
- Kaim, Wolfgang,Lechner-Knoblauch, Ulrike,Haenel, Peter,Bock, Hans
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p. 4206 - 4208
(2007/10/02)
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- Cathodic Birch Reduction of Methoxyaromatics and Steroids in Aqueous Solution
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The electroreduction of methoxybenzene, 1,2,3,4-tetrahydro-6-methoxynaphthalene, and several aromatic steroids using aqueous tetrabutylammonium hydroxide solutions is described.The reactions proceed in high yields, and the corresponding dihydro products are formed.Temperature and electrolyte concentration were found to have a strong effect on the reaction rate.A direct electron transfer to the aromatics is unlikely, and a possible reduction mechanism involving the intermediacy of tetrabutylammonium amalgam is proposed.
- Kariv-Miller, Essie,Swenson, Karl E.,Zemach, Dvora
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p. 4210 - 4214
(2007/10/02)
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- Synthesis of cis-3-hexen-1-ol
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There is provided a novel method of preparing the highly desired odorant cis-3-hexen-1-ol from alkyl phenyl ethers. The method comprises Birch reduction of the alkyl phenyl ether, sequentially followed by oxidative ring cleavage and reduction.
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