- Addition of ketene silyl acetals to the triplet excited state of C60 via photoinduced electron transfer leading to the fullereneacetates
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The photochemical carbon-carbon bond formation of C60 with ketene silyl acetals is described to give a new way for fullerene functionalization chemistry. The photoaddition of ketene silyl acetals to C60 occurs efficiently under irradiation of the visible light in benzene as well as benzonitrile to yield the fullereneacetates. The comparison of the observed rate constants determined from the dependence of the quantum yields on the concentrations of ketene silyl acetals as well as the quenching of triplet excited state of C60 by ketene silyl acetals with those predicted for the electron transfer processes indicates that the photoaddition proceeds via photoinduced electron transfer from ketene silyl acetals to the triplet excited state of C60. The negative shift in the one-electron reduction potentials by the adduct formation of C60 is examined by the cyclic voltammetry measurements. The factors to control the formation of mono- and bisadducts of C60 are clarified based on the rates of photoinduced electron transfer from ketene silyl acetals to the triplet excited states of C60 and the adducts.
- Mikami,Matsumoto,Ishida,Takamuku,Suenobu,Fukuzumi
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- A Disulfonimide Catalyst for Highly Enantioselective Mukaiyama-Mannich Reaction
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A new BINOL-derived chiral disulfonimide has been developed by introducing 4-methyl-3,5-dinitrophenyl substituents at its 3- and 3′-positions. This chiral disulfonimide catalyst displays high catalytic efficacy toward the asymmetric Mukaiyama-Mannich reac
- Zhou, Fengtao,Yamamoto, Hisashi
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- Chiral Modification of the Tetrakis(pentafluorophenyl)borate Anion with Myrtanyl Groups
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The synthesis and characterization of chiral [B(C6F5)4]– derivatives bearing a myrtanyl group instead of a fluoro substituent in the para position are described. These new chiral borates were isolated as their bench-stable lithium, sodium, and cesium salts. The corresponding trityl salts were prepared and tested as catalysts in representative counteranion-directed Diels–Alder reactions and Mukaiyama aldol additions but no enantioselectivity was obtained. Preformation of a chalcone-derived silylcarboxonium ion with the chiral borate as counteranion did not lead to any asymmetric induction in a reaction with cyclohexa-1,3-diene.
- Pommerening, Phillip,Oestreich, Martin
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Read Online
- Preparation method of fexofenadine
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The invention provides a preparation method of fexofenadine, which comprises the following steps: by using bromobenzene as a raw material, carrying out Friedel-Crafts acylation reaction to obtain 4'-bromo-4-chlorophenone ; enabling 4'-bromo-4-chlorobutanone and 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene to subjected to coupling reaction to obtain 2-[4-(4 -chloro-1-butyryl)phenyl]-2-methyl methyl propionate; and sequentially carrying out N-alkylation, carbonyl reduction and alkaline hydrolysis on 2-[4-(4 -chloro-1-butyryl)phenyl]-2-methylpropanoate to obtain fexofenadine. The method has the advantages of cheap and easily available raw materials, easiness in operation, high yield, low cost, no meta-isomer, suitability for industrial production and the like.
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Paragraph 0051; 0067-0069
(2021/04/17)
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- Silanediol versus chlorosilanol: Hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes
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Biphenyl-2,2’-bisfenchyloxydichlorosilane (7, BIFOXSiCl2) is synthesized and employed as precursor for the new silanols biphenyl-2,2’-bisfenchyloxychlorosilanol (8, BIFOXSiCl(OH)) and biphenyl-2,2’-bisfenchyloxysilanediol (9, BIFOXSi(OH)2
- Fox, Falco,Neud?rfl, J?rg M.,Goldfuss, Bernd
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supporting information
p. 167 - 186
(2019/01/30)
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- Asymmetric Total Synthesis of (-)-(3 R)-Inthomycin C
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A short (10 step) and efficient (15% overall yield) synthesis of the natural product (-)-(3R)-inthomycin C is reported. The key steps comprise three C-C bond-forming reactions: (i) a vinylogous Mukaiyama aldol, (ii) an olefin cross-metathesis reaction, and (iii) an asymmetric Mukaiyama-Kiyooka aldol. This route is notable for its brevity and has the advantage of lacking stoichiometric tin-promoted cross-coupling reactions present in previous approaches. Initial investigations on the biological activity of (-)-(3R)-inthomycin C and structural analogues on human cancer cell lines are also described for the first time.
- Balcells, Sandra,Haughey, Maxwell B.,Walker, Johannes C. L.,Josa-Culleré, Laia,Towers, Christopher,Donohoe, Timothy J.
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supporting information
p. 3583 - 3586
(2018/06/26)
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- The Catalytic Asymmetric Mukaiyama–Michael Reaction of Silyl Ketene Acetals with α,β-Unsaturated Methyl Esters
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α,β-Unsaturated esters are readily available but challenging substrates to activate in asymmetric catalysis. We now describe an efficient, general, and highly enantioselective Mukaiyama–Michael reaction of silyl ketene acetals with α,β-unsaturated methyl esters that is catalyzed by a silylium imidodiphosphorimidate (IDPi) Lewis acid.
- Gatzenmeier, Tim,Kaib, Philip S. J.,Lingnau, Julia B.,Goddard, Richard,List, Benjamin
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supporting information
p. 2464 - 2468
(2018/02/06)
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- Eosin Y- and Copper-Catalyzed Dark Reaction to Construct Ene-γ-Lactams
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Eosin Y, a common organo-photocatalyst in visible-light photoredox processes, was found to show excellent catalytic activities for thermal redox reactions under a catalytic amount of Cu(OAc)2. With this catalytic system, vinyl azides and ketene silyl acetals combine to form formal [3 + 2] cycloadducts by α-ester radical addition without light irradiation. This method provides a mild and straightforward paradigm to prepare important synthons of five-membered ene-γ-lactams and bridge ring lactams. It is the first example of an eosin Y-catalyzed redox reaction in the dark.
- Lei, Wen-Long,Feng, Kai-Wen,Wang, Tao,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 7220 - 7224
(2018/11/25)
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- Synthesis of Conformationally Constrained Esters and Amines by Pd-Catalyzed α-Arylation of Hindered Substrates
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The α-arylation of sterically hindered silyl ketene acetals (SKAs) with sterically hindered aryl bromides occurs efficiently using Pd[P(t-Bu)3]2 as the optimal catalyst and ZnF2 as a promoter. Less sensitive P(t-Bu)3
- Martin, Anthony,Vors, Jean-Pierre,Baudoin, Olivier
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p. 3941 - 3945
(2016/07/06)
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- Pestalotiopsin A. Enantioselective construction of potential building blocks derived from antipodal cyclobutanol intermediates
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(Chemical Equation Presented) D-Glyceraldehyde acetonide has been used as the starting point for accessing the enantiomeric cyclobutanols 11 in optically pure condition. The dextrorotatory enantiomer has been transformed in five steps into the [3.2.0] bic
- Paquette, Leo A.,Parker, Gregory D.,Tei, Takahiro,Dong, Shuzhi
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p. 7124 - 7134
(2008/02/11)
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- In pursuit of pestalotiopsin A via zirconocene-mediated ring contraction
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An asymmetric route from the epimeric β-hydroxy esters 4 and 5 to the densely functionalized (+)-10 and (-)-10, respectively, is described. Either cyclobutanol can be made available as the predominant product. The levorotatory antipode has been transforme
- Dong, Shuzhi,Parker, Gregory D.,Tei, Takahiro,Paquette, Leo A.
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p. 2429 - 2431
(2007/10/03)
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- ASYMMETRIC-SYNTHESIS CATALYST BASED ON CHIRAL BROENSTED ACID AND METHOD OF ASYMMETRIC SYNTHESIS WITH THE CATALYST
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A compound usable as an asymmetric synthesis catalyst which can be easily synthesized without using any metal such as a lanthanoid group element; a method of asymmetric synthesis with the compound; and a chiral compound obtained by the asymmetric synthesis method. A Broensted acid is used as a catalyst in asymmetric synthesis, the chiral Broensted acid being represented by formula (1) below or formula (3) below. The asymmetric synthesis method employs the catalyst. Asymmetric synthesis with the catalyst gives a chiral compound.
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Page/Page column 25
(2010/11/08)
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- Reaction of silyl ketene acetals with epoxides: A new method for the synthesis of γ-butanolides
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Titanium tetrachloride promoted reaction of silyl ketene acetals with epoxides, followed by acidic work-up, affords butanolides in moderate/good yields. With epihalohydrins the reaction is regioselective and occurs at the less substituted end of the epoxide; the γ-haloalkyl-γ-butanolides thus obtained can be further transformed into various products. Graphical Abstract
- Maslak, Veselin,Matovi?, Radomir,Sai?i?, Radomir N.
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p. 8957 - 8966
(2007/10/03)
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- Surface-mediated solid phase reaction. Part 9. A convenient procedure for aldol reaction of ketene silyl acetals with aldehydes on the solid surface of alumina
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The aldol reaction of ketene silyl acetals with aldehydes proceeds efficiently on the solid surface of alumina impregnated with anhydrous zinc chloride under sonication providing aldol products in high yields and with good stereoselectivity.
- Ranu, Brindaban C.,Saha, Manika,Bhar, Sanjay
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p. 3065 - 3077
(2007/10/03)
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- 2-(N-Methylanilino)-2-phenylsulfanylacetonitrile, A Reagent Tested for Electrophilic, Nucleophilic, and Radical Reactions
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2-(N-Methylanilino)-2-phenylsulfanylacetonitrile 1 has been readily prepared from 2-(N-methylanilino)acetonitrile and diphenyl disulfide.Alkylation of the anion of 1 with halogenoalkanes resulted in concurrent elimination of benzenethiol to give conjugated α-aminoalkenenitriles of 2E-configuration.Autoxidation of 1 in the presence of alkoxide ions afforded alkyl N-methyl-N-phenylcarbamates.Nucleophilic substitution of 1 with Grignard reagent or appropriate silyl compounds were promoted by CuI or Lewis acids to give varied α-amino nitriles.The 4-oxo-2-aminonitriles 9 obtained by condensation of 1 and titanium enolates can be considered as derivatives of 1,3-dicarbonyl compounds with the aldehyde group being activated to give an amino nitrile umpolung.When 1 was treated with tributylstannane, the corresponding amino nitrile α-radical was formed and the self-coupling product was isolated.
- Chen, Chih-Cheng,Chen, Same-Ting,Chuang, Tsung-Hsun,Fang, Jim-Min
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p. 2217 - 2222
(2007/10/02)
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- Electron Transfer Profile of Cyclopropanone Acetals in the Nonirradiated Reaction with Tetracyanoethylene, Chloranil, and Dicyanodichlorobenzoquinone
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The donor profiles of cyclopropanone acetals 1 and 2 were examined in the reactions with electron acceptors (TCNE, DDQ, chloranil, and 1-cyanonaphthalene).With TCNE under nonirradiating conditions, an exclusive 2 + 2 cycloaddition took place stereospecifically with monosubstituted acetals 1a-c but nonstereospecifically with disubstituted acetals 1d,e.With quinones, a ring-opening of the cyclopropane and its coupling with the quinone took place to give the C (cyclopropane)-O (quinone) adduct 9 (with chloranil) or 10 (with DDQ), the latter of which underwent the elimination of a phenol to produce unsaturated esters 5 and 6.In addition, the intervention of the C (cyclopropane)-C (quinone) adduct 14 (with chloranil) or 15 (with DDQ), both as the precursor of 5 and 6, was also postulated.With 1-cyanonaphthalene, under photolysis, the cis/trans isomerization of 1 and 2 occured.The results provided evidences that cyclopropanone acetals, in general, are prone to function as donors.The mechanism of the reaction with quinones, in particular, was investigated in detail.
- Oku, Akira,Abe, Manabu,Iwamoto, Masaharu
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p. 7445 - 7452
(2007/10/02)
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- The Synthesis of O-Silyl Ketene Acetals from α-Haloesters
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α-Haloesters of the general structure R1R2CXCO2R3 1 have been shown to react with sodium in the presence of a halosilane 2 to yield the corresponding O-silyl ketene acetals 3 (SKAs) according to equation 4.The factor that most influences the yields in these reactions is the concentration of halosilane; if there is a deficiency of halosilane, then acyloin condensation products will detract from the yield of SKAs.The reaction is quite general, and often gives yields in excess of 90percent of the desired SKAs.
- Schulz, William J.,Speier, John L.
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p. 163 - 166
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, VI. - Synthesis of 2-Heterosubstituted O-Alkyl-O-(trimethylsilyl)ketene Acetals and 2-(Trimethylsilyl)carboxylates
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Organooxy- and (alkylthio)ethanoic acid esters 2 are silylated by trimethylsilyl triflate (1) in the presence of triethylamine to yield mixtures of ketene acetals 3 and 2-(trimethylsilyl)ethanoates 4.The product distributions 3/4 are governed by the ester groups and the substituents in α position.Cyclic derivatives of 2-hydroxycarboxylic acids 7,9 are silylated by 1/triethylamine to give the ketene acetals 8,10.From N-protected glycine methyl esters 11,12 the ketene acetals 13,15 are obtained in the reaction with 1/triethylamine.
- Oesterle, Thomas,Simchen, Gerhard
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p. 687 - 692
(2007/10/02)
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- NOVEL SYNTHESIS OF β-SILOXY ESTERS BY CONDENSATION OF CARBONYLS AND TRIMETHYLSILANE WITH α,β-UNSATURATED ESTERS CATALYZED BY RhCl3
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A novel one pot reaction of α,β-unsaturated esters with carbonyls and trimethylsilane gave good yields of β-siloxy esters.This RhCl3 catalyzed method improves upon the two step reaction of silyl ketene acetals with carbonyls.
- Revis, Anthony,Hilty, Terrence K.
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p. 4809 - 4812
(2007/10/02)
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- Synthesis of 3-(4'-Methoxyphenyl)-2,2,4,4-tetramethylpentane and Some Cyclic Analogues
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Reaction of 1-methoxy-2-methyl-1-trimethylsilyloxyprop-1-ene (8) with 1-acetoxy-1-(4'-methoxyphenyl)-2,2-dimethylpropane (7b) in the presence of zinc iodide gave 84percent of methyl 3-(4'-methoxyphenyl)-2,2,4,4-tetramethylpentanoate (9a), which was reduce
- Collins, David J.,Jacobs, Howard A.
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p. 2095 - 2110
(2007/10/02)
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- 1,3-Dithienium- and 1,3-Dithiolenium Salts, III. Synthesis of Cyclic Dithioacetals of β-Keto Esters from Ketene Silyl Acetals
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The 1,3-dithian-2-ylium tetrafluoroborates 3, available by different methods, react in good yields with the ketene silyl acetals 2 to give the new cyclic dithioacetals 4 which are deacetalized to the β-keto esters 5 and 9.
- Stahl, Ingfried
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p. 3159 - 3165
(2007/10/02)
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- Addition of Ketene Trimethylsilyl Acetals to α,β-Unsaturated Ketones: A New Strategy for Michael Addition of Ester Enolates
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Trialkylsilyl ketene acetals in the presence of tris(dimethylamino)sulfonium difluorotrimethylsiliconate generate very potent carbon nucleophiles formally equivalent to ester enolates.In sharp contrast to the commonly used lithium enolates, these acetals
- RajanBabu, T. V.
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p. 2083 - 2089
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, II. - Synthesis of O-Alkyl-O-(trialkylsilyl)ketene Acetals and 2-(Trialkylsilyl)carboxylates
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Alkyl carboxylates 2 are silylated by trialkylsilyl triflates 1 in the presence of triethylamine (3) to yield ketene acetals 4.In reactions of the esters 6 mixtures of ketene acetals 7 and at the α-carbon silylated esters 8 are obtained.Ethanoic acid esters and lactones are doubly silylated to give the products 11, 12, and 15, respectively.Under suitable conditions silylation of the esters 10 gives rise to the 2-trimethylsilylethanoic acid esters 13.The thermodynamically more stable products are obtained.Product distributions depend on the structure of the esters and the silylating agents 1.
- Emde, Herbert,Simchen, Gerhard
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p. 816 - 834
(2007/10/02)
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- Oxidation of Alkyl Trimethylsilyl Ketene Acetals with Lead(IV)
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Alkyl trimethylsilyl ketene acetals generated from either esters or lactones react with lead(IV) acetate (LTA) or lead(IV) benzoate (LTB) to afford useful yields of the corresponding α-carboyloxy esters and α-carboyloxy lactones.Yields of the reaction products are optimized by use of the appropriate solvent (methylene chloride or benzene) during oxidation.Alkyl groups such as methyl, ethyl, and tert-butyl are all compatible with the procedure, and lactones containing five-, six-, and seven-membered rings give good yields of oxidation products.
- Rubottom, George M.,Gruber, John M.,Marrero, Roberto,Juve, Henrik D.,Kim, Wan Chong
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p. 4940 - 4944
(2007/10/02)
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- ALKYLATION DE QUELQUES COMPOSES CARBONYLES PAR DES GROUPES TERTIAIRES. UTILISATION DE LA REACTION DE FRIEDEL-CRAFTS DANS LA SYNTHESE D'ESTERS ET DE CETONES ENCOMBRES
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t-Alkylation of carboxylic esters via their ketene alkyl trimethylsilyl acetels by the Friedel-Crafts reaction allows the synthesis of new higly hindered compounds.A new route using sodium amide in dimethoxyethane, for the preparation of trimethylsilyl enol ethers of ketones, is described.The α-butylation of these compounds permits the synthesis of new crowded pentasubstituted ketones.The limits as well as the performance of the method have been studied.
- Lion, Claude,Dubois, Jacques-Emile
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p. 319 - 323
(2007/10/02)
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