- Regioselective Wacker-Type Oxidation of Internal Olefins in tBuOH Using Oxygen as the Sole Oxidant and tBuONO as the Organic Redox Cocatalyst
-
A regioselective Wacker-Tsuji oxidation of internal olefins in tBuOH has been developed using oxygen as the terminal oxidant and tert-butyl nitrite as the simple organic redox cocatalyst without the involvement of hazardous cocatalysts or harsh reaction conditions. A series of internal olefins bearing various functional groups can be oxidized to the corresponding substituted ketones in generally good yields with high regioselectivities.
- Huang, Qing,Li, Ya-Wei,Ning, Xiao-Shan,Jiang, Guo-Qing,Zhang, Xiao-Wei,Qu, Jian-Ping,Kang, Yan-Biao
-
supporting information
p. 965 - 969
(2020/02/15)
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- Aerobic Acyloxylation of Allylic C?H Bonds Initiated by a Pd0 Precatalyst with 4,5-Diazafluoren-9-one as an Ancillary Ligand
-
Palladium-catalyzed allylic C?H oxidation has been widely studied, but most precedents use acetic acid as the coupling partner. In this study, a method compatible with diverse carboxylic acid partners has been developed. Use of a Pd0 precatalyst under aerobic reaction conditions leads to oxidation of Pd0 by O2 in the presence of the desired carboxylic acid to generate a PdII dicarboxylate that promotes acyloxylation of the allylic C?H bond. Good-to-excellent yields are obtained with a roughly 1:1 ratio of the alkene and carboxylic acid reagents. Optimized reaction conditions employ 4,5-diazafluoren-9-one (DAF) as a ligand, in combination with a quinone/iron phthalocyanine cocatalyst system to support aerobic catalytic turnover.
- Kozack, Caitlin V.,Sowin, Jennifer A.,Jaworski, Jonathan N.,Iosub, Andrei V.,Stahl, Shannon S.
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p. 3003 - 3007
(2019/06/17)
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- Systematic Evaluation of Sulfoxides as Catalysts in Nucleophilic Substitutions of Alcohols
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Herein, a method for the nucleophilic substitution (SN) of benzyl alcohols yielding chloro alkanes is introduced that relies on aromatic sulfoxides as Lewis base catalysts (down to 1.5 mol-%) and benzoyl chloride (BzCl) as reagent. A systematic screening of various sulfoxides and other sulfinyl containing Lewis bases afforded (2-methoxyphenyl)methyl sulfoxide as optimal catalyst. In contrast to reported formamide catalysts, sulfoxides also enable the application of plain acetyl chloride (AcCl) as reagent. In addition, it was demonstrated that weakly electrophilic carboxylic acid chlorides like BzCl promote Pummerer rearrangement of sulfoxides already at room temperature. This side-reaction also provided the explanation, why sulfoxide catalyzed SN-reactions of alcohols do not allow the effective production of aliphatic and electron deficient chloro alkanes. Comparison experiments provided further insight into the reaction mechanism.
- Motsch, Sebastian,Schütz, Christian,Huy, Peter H.
-
supporting information
p. 4541 - 4547
(2018/09/13)
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- Transition-Metal-Free Poly(thiazolium) Iodide/1,8-Diazabicyclo[5.4.0]undec-7-ene/Phenazine-Catalyzed Esterification of Aldehydes with Alcohols
-
Poly(3,4-dimethyl-5-vinylthiazolium) iodide was used as a polymer precatalyst in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and phenazine for the oxidative esterification of aldehydes with alcohols. Selective functionalization of OH groups was achieved in the presence of NH2 groups. The poly(thiazolium) iodide/DBU/phenazine system exhibited excellent catalytic activity and could be reused five times without loss of activity.
- Chun, Supill,Chung, Young Keun
-
supporting information
p. 3787 - 3790
(2017/07/26)
-
- Iridium-Catalyzed Enantioselective Allylic Substitution of Aliphatic Esters with Silyl Ketene Acetals as the Ester Enolates
-
Enantioselective allylic substitution with enolates derived from aliphatic esters under mild conditions remains challenging. Herein we report iridium-catalyzed enantioselective allylation reactions of silyl ketene acetals, the silicon enolates of esters, to form products containing a quaternary carbon atom at the nucleophile moiety and a tertiary carbon atom at the electrophile moiety. Under relatively neutral conditions, the allylated aliphatic esters were obtained with excellent regioselectivity and enantioselectivity. These products were readily converted into primary alcohols, carboxylic acids, amides, isocyanates, and carbamates, as well as tetrahydrofuran and γ-butyrolactone derivatives, without erosion of enantiomeric purity.
- Jiang, Xingyu,Hartwig, John F.
-
p. 8887 - 8891
(2017/07/17)
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- Highly efficient nitrogen chelated ruthenium carbene metathesis catalysts
-
A series of nitrogen chelated ruthenium carbene metathesis catalysts containing an N-heterocyclic carbene (NHC) and a carbonyl group have been developed and their catalytic activities for olefin metathesis reactions were investigated. The X-ray structure of the [(H2IMes)(Cl)2Ru]C(H)CH2[p-F(C6H3)NC(CF3)(C(O)OCH2CH3)] complex shows that the carbonyl oxygen of the ester and the imine nitrogen are both coordinated to the Ru metal to give an octahedral structure. The catalytic activity of these ruthenium carbene complexes for olefin metathesis reactions was tested. Some of the complexes bearing electron withdrawing groups had high initiation rates. These complexes exhibited excellent performance for both ring-closing metathesis and cross metathesis.
- Duan, Yulian,Wang, Tao,Xie, Qingxiao,Yu, Xiaobo,Guo, Weijie,Wang, Jianhui,Liu, Guiyan
-
p. 19441 - 19448
(2016/12/16)
-
- METHOD OF CONVERTING ALCOHOL TO HALIDE
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The present invention relates to a method of converting an alcohol into a corresponding halide. This method comprises reacting the alcohol with an optionally substituted aromatic carboxylic acid halide in presence of an N-substituted formamide to replace a hydroxyl group of the alcohol by a halogen atom. The present invention also relates to a method of converting an alcohol into a corresponding substitution product. The second method comprises: (a) performing the method of the invention of converting an alcohol into the corresponding halide; and (b) reacting the corresponding halide with a nucleophile to convert the halide into the nucleophilic substitution product.
- -
-
Page/Page column 50; 107; 108
(2017/01/02)
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- A six-coordinated cationic ruthenium carbyne complex with liable pyridine ligands: Synthesis, structure, catalytic investigation, and DFT study on initiation mechanism
-
A novel six-coordinated high-valence cationic ruthenium carbyne complex bearing two liable pyridine ligands was prepared in high yield by the reaction of the ruthenium-based complex (IMesH2)(Cl)2(C 5H5N)2RuCHPh [IMesH2=1,3-dimesityl- 4,5-dihydroimida-zol-2-ylidene] with excess iodine as an oxidant in CH 2Cl2 at 25 °C under N2. The new ruthenium carbyne-based complex shows moderate to good catalytic activity for ring-closing metathesis reactions. Importantly, no double bond isomerization by-product was produced at elevated reaction temperatures (100 °C-137 °C) in the reaction catalyzed by the synthesized ruthenium carbyne complex. A mechanism involving the in situ conversion of the ruthenium carbyne through the addition of an iodide to the carbyne carbon was also proposed, and DFT calculations were performed to explain the initiating mechanism.
- Liu, Guiyan,Zheng, Lu,Shao, Mingbo,Zhang, Huizhu,Qiao, Weixia,Wang, Xiaojia,Liu, Bowen,Zhao, Haitao,Wang, Jianhui
-
supporting information
p. 4718 - 4725
(2014/06/24)
-
- Modified Yamaguchi reagent: Convenient and efficient esterification
-
A convenient and efficient esterification method that used a modified Yamaguchi reagent (2,4,6-trichlorobenzoyl chloride-4-dimethylaminopyridine) and avoided use not only of intractable acid chloride but also of acid anhydrides was proposed. The reaction mechanism was described by Fourier transform infrared spectroscopy and supported by a density functional theory calculation.
- Okuno, Yoshinori,Isomura, Shigeki,Nishibayashi, Akihiro,Hosoi, Aiko,Fukuyama, Kei,Ohba, Masashi,Takeda, Kazuyoshi
-
supporting information
p. 2854 - 2860
(2014/10/15)
-
- Synthesis of acyclic ketones by catalytic, bidirectional homologation of formaldehyde with nonstabilized diazoalkanes. Application of a chiral diazomethyl(pyrrolidine) in total syntheses of erythroxylon alkaloids
-
This work offers a catalytic approach to convergent ketone assembly based upon formal and tandem C-H insertion of diazoalkanes in the presence of limiting amounts of monomeric formaldehyde, which is easily generated as a gas by thermolysis of the inexpensive and abundant paraformaldehyde (~30 USD/kg). The method forms di-, tri-, and even tetrasubstituted acetones with high efficiency, and it has streamlined a synthesis of (-)-dihydrocuscohygrine in which the absolute stereochemistry of a proline-based starting material is preserved. Assisted by the advent of new protocols for hydrazone oxidation, we also provide full details on handling non-carbonyl-stabilized diazo compounds.
- Wommack, Andrew J.,Kingsbury, Jason S.
-
p. 10573 - 10587
(2013/11/19)
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- A unique ruthenium carbyne complex: A highly thermo-endurable catalyst for olefin metathesis
-
A cationic ruthenium carbyne complex was prepared and was found to initiate olefin metathesis reactions with good activities, which throws a new light on the design of a new type of ruthenium catalyst for RCM reactions. More importantly, no double bond isomerized by-product was observed even at elevated temperatures in reactions catalyzed by the new carbyne complex. A mechanism involving the in situ conversion of the ruthenium carbyne to a ruthenium carbene complex via addition of an iodide to the carbyne carbon was also proposed.
- Wang, Jianhui,Shao, Mingbo,Zheng, Lu,Qiao, Weixia,Wang, Jingjing
-
supporting information
p. 2743 - 2750,8
(2012/12/12)
-
- Synthesis, structure and catalytic study of chloro-bridged two-core ruthenium carbene complexes
-
The reaction of a ruthenium carbide complex RuCl2(C:) (PCy 3)2 with [H(Et2O)x] +[BF4]- at a molar ratio of 1:2 produced a two-core ruthenium carbene complex {[RuCl(CHPCy3)(PCy 3)]2(μ-Cl)3}+·[BF 4]- (8) in the form of a yellow-green crystalline solid. After a ligand exchange reaction of 8 with LiBr, a bromide ruthenium carbene complex {[RuBr(CHPCy3)(PCy3)]2(μ-Cl) 3}+·[BF4]- (9) was obtained as a crystalline solid. Catalytic studies showed that both 8 and 9 are selective catalysts for ring closing metathesis of unsubstituted terminal dienes. More importantly, no isomerized byproduct was observed when 8, or 9 was used as the catalyst at an elevated temperature (137 °C), indicating that both 8 and 9 are chemo-selective catalysts for ring closing metathesis reactions.
- Qiao, Weixia,Shao, Mingbo,Wang, Jianhui
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experimental part
p. 197 - 202
(2012/08/27)
-
- Titration of nonstabilized diazoalkane solutions by fluorine NMR
-
A new protocol for titrating nonstabilized diazoalkane solutions by quantitative 19F NMR is reported. An excess of 2-fluorobenzoic acid dissolved in CDCl3 is treated with the diazoalkane solution at a low temperature, immediately forming the corresponding 2-fluorobenzoate ester upon warming. A significant difference in the 19F chemical shift between the ester and acid is seen, allowing facile and accurate integration to determine titer. The procedure is safe, rapid, and indicates the active diazoalkane concentration with high precision.
- Rendina, Victor L.,Kingsbury, Jason S.
-
experimental part
p. 1181 - 1185
(2012/03/12)
-
- Synthesis of 1,3-diarylpropenes through palladium-catalyzed mizoroki-heck and allyl cross-coupling reactions using hydrazones as ligands
-
The palladium-catalyzed synthesis of unsymmetrical 1,3-diarylpropenes from allyl esters through a Mizoroki-Heck-type reaction with aryl iodides followed by allyl cross-coupling with a variety of arylboronic acids was developed; the products are obtained in moderate to good yields by using a hydrazone-Pd(OAc) 2 system. The synthesis of unsymmetrical 1,3-diarylpropenes from allyl esters by a Mizoroki-Heck-type reaction followed by allyl cross-coupling with a variety of arylboronic acids was developed; the products were obtained in moderate to good yields by using a hydrazone-Pd(OAc)2 system. Copyright
- Mino, Takashi,Koizumi, Tomoko,Suzuki, Saori,Hirai, Kiminori,Kajiwara, Kenji,Sakamoto, Masami,Fujita, Tsutomu
-
supporting information; experimental part
p. 678 - 680
(2012/03/10)
-
- Pd(II)-catalyzed direct olefination of arenes with allylic esters and ethers
-
A convenient Pd(II)-catalyzed direct olefination of unactivated arenes with allylic esters and ethers via C-H activation was demonstrated. Under the typical conditions, various aryl-substituted allylic esters and ethers can be prepared. Georg Thieme Verlag Stuttgart - New York.
- Shang, Xiaojie,Xiong, Yun,Zhang, Yuexia,Zhang, Lei,Liu, Zhongquan
-
supporting information; experimental part
p. 259 - 262
(2012/03/08)
-
- A non-heme iron(III) complex with porphyrin-like properties that catalyzes asymmetric epoxidation
-
In this report, we describe an iron(III) complex containing a carbazole-based tridentate ligand that catalyzes highly enantioselective asymmetric epoxidation of (E)-alkenes at room temperature. The non-heme iron(III) complex has a five-coordinated trigonal-bipyramidal structure, and its two-electron oxidized state has the similar electronic structure as that of iron porphyrins.
- Niwa, Takashi,Nakada, Masahisa
-
supporting information; experimental part
p. 13538 - 13541
(2012/10/08)
-
- Pt(IV)-catalyzed generation and [4+2]-cycloaddition reactions of o-quinone methides
-
Novel intermolecular and intramolecular generations of ortho-quinone methides and their formal [4+2]-cycloaddition reactions with olefins catalyzed by PtCl4 and AuCl3 under mild conditions have been developed. Good to excellent yields (up to 99%) and diastereoselectivity (up to >99:1) of the chromans were obtained. PtCl4 was found to be effective and compatible with various functional groups present in the substrates. A mechanism accounting for its catalytic cycle is proposed and discussed.
- Radomkit, Suttipol,Sarnpitak, Pakornwit,Tummatorn, Jumreang,Batsomboon, Paratchata,Ruchirawat, Somsak,Ploypradith, Poonsakdi
-
supporting information; experimental part
p. 3904 - 3914
(2011/06/22)
-
- Cl3CCONH2/PPh3: A versatile reagent for synthesis of esters
-
Cl3CCONH2/PPh3 was a versatile reagent to convert carboxylic acids into their corresponding acid chlorides. This intermediate was clearly confirmed by spectroscopic methods (IR, 1H, 13C NMR). This one-pot reaction of in situ acid chloride generated with various alcohols successfully furnished the corresponding esters in moderate to excellent yields. Copyright ? Taylor & Francis Group, LLC.
- Chantarasriwong, Oraphin,Jang, Doo Ok,Chavasiri, Warinthorn
-
scheme or table
p. 2845 - 2856
(2009/04/11)
-
- [(NHC)Au1]-catalyzed rearrangement of allylic acetates
-
Equation Presented [(NHC)AuCl] complexes (NHC = N-heterocyclic carbene), in conjunction with a silver salt, were found to efficiently catalyze the rearrangement of allylic acetates under both conventional and microwave-assisted heating. The optimization of several reaction parameters (solvent, silver salt, and ligand) as well as a study of the reaction scope are reported. The steric hindrance of the ligand bound to gold was found crucial for the outcome of the reaction as only extremely bulky ligands permitted the isomerization.
- Marion, Nicolas,Gealageas, Ronan,Nolan, Steven P.
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p. 2653 - 2656
(2008/02/09)
-
- N, O-ligand accelerated zinc-catalyzed transesterification of alcohols with vinyl esters
-
N-Phenyldiethanolamine (1f) is an efficient ligand for zinc-catalyzed transesterification of alcohols with vinyl acetate (R3 = Me) at room temperature. In the case of using other vinyl esters (R3 = Et, n-Pr, Ph), the corresponding products were easily obtained in the presence of pyridine-type ligand 2 instead of aminoalcohol 1f.
- Mino, Takashi,Hasegawa, Tae,Shirae, Yoshiaki,Sakamoto, Masami,Fujita, Tsutomu
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p. 4389 - 4396
(2008/02/13)
-
- Enantioselective oxidation of olefins catalyzed by chiral copper bis(oxazolinyl)pyridine complexes: A reassessment
-
Copper complexes of chiral tridentate pybox ligands synthesized using a modified procedure have been studied as catalysts for the enantioselective allylic oxidation of olefins. A variety of olefins have been used in this reaction. Using 5 mol% of a Cu(II)
- Ginotra, Sandeep K.,Singh, Vinod K.
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p. 3573 - 3581
(2007/10/03)
-
- Sulfoxides in Julia-Lythgoe olefination: Efficient and stereoselective preparation of di-, tri-, and tetrasubstituted olefins
-
(Chemical Equation Presented) A novel modification of the classical Julia-Lythgoe olefination, using sulfoxides instead of sulfones, affords, after in situ benzoylation and Sml2/HMPA- or DMPU-mediated reductive elimination, 1,2-di-, tri-, and tetrasubstituted olefins in moderate to excellent yields and E/Z selectivity. The conditions are mild, and the procedure is broadly applicable.
- Pospisil, Jiri,Pospisil, Tomas,Marko, Istvan E.
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p. 2373 - 2376
(2007/10/03)
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- Sulfoxide-modified Julia-Lythgoe olefination: Highly stereoselective di-, tri-, and tetrasubstituted double bond formation
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A novel modification of the classical Julia-Lythgoe olefination, using sulfoxides instead of sulfones, affords, after in situ benzoylation and SmI 2/HMPA or SmI2/DMPU-mediated reductive elimination, 1,2-di-, tri- and tetrasubstituted olefins in moderate to good yields and E/Z selectivity. The conditions are mild and the procedure is widely applicable. The reaction mechanism was studied and a general model, describing the reaction selectivity, is proposed.
- Pospisil, Jiri,Pospisil, Tomas,Marko, Istvan E.
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p. 1953 - 1969
(2007/10/03)
-
- A rapid microwave-assisted esterification utilizing the Mukaiyama supported reagent
-
Microwave heating was applied to a modified Mukaiyama reagent supported on a PS-DVB resin to develop a rapid and efficient protocol for the solution-phase synthesis of esters and lactones starting from alcohol and carboxylic acids. The products were obtained in high purity (NMR analysis) after a simple resin filtration.
- Donati, Donato,Morelli, Costanza,Taddei, Maurizio
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p. 2817 - 2819
(2007/10/03)
-
- Nucleophilic acyl substitutions of anhydrides with protic nucleophiles catalyzed by amphoteric, oxomolybdenum species
-
(Chemical Equation Presented) Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO2Cl2 adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-α-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl2(O2-CBu t)2 between pivalic anhydride and MoO2Cl 2 as the catalyst.
- Chen, Chien-Tien,Kuo, Jen-Huang,Pawar, Vijay D.,Munot, Yogesh S.,Weng, Shieu-Shien,Ku, Cheng-Hsiu,Liu, Cheng-Yuan
-
p. 1188 - 1197
(2007/10/03)
-
- A green protocol for chemoselective O-acylation in the presence of zinc oxide as a heterogeneous, reusable and eco-friendly catalyst
-
The solvent-free acylation of alcohols and phenols with acyl chlorides using ZnO as a catalyst is described. The remarkable selectivity under mild and neutral conditions, and recyclability of the catalyst, are advantages.
- Tamaddon, Fatemeh,Amrollahi, Mohammad Ali,Sharafat, Leily
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p. 7841 - 7844
(2007/10/03)
-
- Iron perchlorate on silica gel as multi-purpose reagent for catalysis of closure and rupture of carbon-oxygen bond in epoxides, alcohols, and esters
-
Aliphatic alcohols and water in the presence of catalytic amounts of Fe3+ ion introduced as iron(III) perchlorate on silica gel carrier perform efficient regiospecific opening of an epoxy ring. Carbon acids esterification with various type alcohols was carried out using the system Fe(ClO4)3-silica gel in dichloromethane under conditions excluding solvolysis. Acetylation and formylation of alcohols was performed by efficient transesterification with ethyl acetate and ethyl formate.
- Salechi,Khodaei,Ghareghani,Motlagh
-
p. 794 - 796
(2007/10/03)
-
- Efficient transesterification/acylation reactions mediated by N-heterocyclic carbene catalysts
-
Imidazol-2-ylidenes, a family of N-heterocyclic carbenes (NHC), are efficient catalysts in the transesterification involving numerous esters and alcohols. Low catalyst loadings of aryl- or alkyl-substituted NHC catalysts mediate the acylation of alcohols with enol acetates in short reaction times at room temperature. Commercially available and more difficult to cleave methyl esters react with primary alcohols in the presence of alkyl-substituted NHC to efficiently form the corresponding esters. While primary alcohols are selectively acylated over secondary alcohols with use of enol esters as acylating agents, methyl and ethyl esters can be employed as protective agents for secondary alcohols in the presence of the more active alkyl-substituted NHC catalysts. The NHC-catalyzed transesterification protocol was simplified by generating the imidazol-2-ylidene catalysts in situ.
- Grasa, Gabriela A.,Gueveli, Tatyana,Singh, Rohit,Nolan, Steven P.
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p. 2812 - 2819
(2007/10/03)
-
- Palladium-catalyzed coupling of alkynes with alcohols and carboxylic acids
-
The palladium-catalyzed coupling of alkynes with alcohols and carboxylic acids to give allylic ethers and esters has been achieved. With phenols, these conditions furnish the C-alkylation products.
- Zhang, Weijiang,Haight, Anthony R.,Hsu, Margaret C.
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p. 6575 - 6578
(2007/10/03)
-
- Rapid and reusable copper catalytic system for allylic oxidation of olefins in hexafluoroisopropanol as solvent
-
Cu2O mixed with perfluorododecanoic acid C11F23COOH and t-butyl peroxybenzoate in hexafluoroisopropanol led to a rapid and reusable catalytic system for the Kharasch-Sosnovsky reaction.
- Fache, Fabienne,Piva, Olivier
-
p. 2035 - 2036
(2007/10/03)
-
- Selective sulfonylation of arenes and benzoylation of alcohols using lithium perchlorate as a catalyst under neutral conditions
-
Sulfonylation of aromatics with p-toluenesulfonyl chloride and benzoylation of alcohols with benzoyl chloride using lithium perchlorate as a catalyst is described. The remarkable selectivity under neutral conditions is an attractive feature of this method.
- Bandgar,Kamble,Sadavarte,Uppalla
-
p. 735 - 738
(2007/10/03)
-
- Palladium-catalyzed arylation of allylic benzoates using hypervalent siloxane derivatives
-
Palladium-catalyzed cross-coupling of hypervalent arylsiloxane derivatives proceeded in good to excellent yields with allylic benzoates. Arylation occurred with complete inversion of configuration. The scope and limitations of this reaction, an alternative to the Stille coupling, is summarized.
- Correia,DeShong
-
p. 7159 - 7165
(2007/10/03)
-
- Bismuth(III) salts as convenient and efficient catalysts for the selective acetylation and benzoylation of alcohols and phenols
-
Efficient acetylation and benzoylation of alcohols and phenols with acetic and benzoic anhydrides have been carried out under catalysis of bismuth(III) salts including BiCl3, Bi(TFA)3 and Bi(OTf)3. Selective acetylation and benzoylation of alcohols in the presence of phenols is an additional advantage of this procedure.
- Mohammadpoor-Baltork, Iraj,Aliyan, Hamid,Reza Khosropour, Ahmad
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p. 5851 - 5854
(2007/10/03)
-
- P(RNCH2CH2)3N: Efficient catalysts for transesterifications, acylations, and deacylations
-
Extremely strong nonionic superbases of the type P(RNCH2CH2)3N catalyze the transesterification of carboxylic acid esters with high selectivity and yields at 25 °C. These bases also catalyze the deacetylation of alcohols under mild conditions in quantitative yields. Using enol acetates as acylating agents, primary and secondary alcohols are efficiently protected as acetates through the action of these catalysts. Substituents such as epoxide, carbamate, acetal, oxazoline, nitro, and alkynyl functionalities are tolerated under the reaction conditions. N-Protected peptides undergo clean transesterification without significant racemization, making this methodology potentially very useful.
- Ilankumaran, Palanichamy,Verkade
-
p. 3086 - 3089
(2007/10/03)
-
- Unsymmetrical Ketone Synthesis via a Three-Component Connection Reaction of Organozincs, Allylating Agents, and Carbon Monoxide
-
A wide variety of organozincs (diethylzinc, alkylzinc halides, and organozincs 2, 5, and 9a-e, functionalized with ester and nitrile groups) undergo a three-component connection reaction with carbon monoxide and allylic benzoates or phosphates 1a-h to furnish unsymmetrical ketones, e.g., 3, 6, and 10, in good yields uder 1 atm of carbon monoxide at ambient temperature by the catalysis of tetrakis(triphenylphosphine)palladium in THF/HMPA.The regio- and stereoselectivities of the present carbonylation show marked contrast to those reported for the palladium-catalyzed carbonylation of usymmetrical allylic substrates.For example, the reaction of crotyl benzoate with octylzinc iodide provides all the possible stereo- and regioisomers, i.e., cis- and trans-2-butenyl and 1-methyl-2-propenyl octyl ketones in comparable amounts.The carbonylative coupling of carvyl phosphates, trans- and cis-1h, and γ-zincio ester 5 is stereospecific and proceeds with inversion of configuration at the allylic stereocenters to furnish cis- and trans-6h, respectively, as single diastereomers.In the absence of HMPA, the reaction feature changes dramatically and lactones 12 and 13 (composed of organozincs, carbon monoxide, and allylating agents in the ratios of 1:1:2 and 2:1:1, respectively) and symmetrical keto diesters 14 (composed of 2 mol of organozincs and 1 mol of carbon monoxide) are formed in varying ratios depending on the reaction conditions.Synthetic scope of the unsymmetrical ketones and mechanistic rationale for these unique and unprecedented reaction behaviors are discussed.
- Yasui, Kengo,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao
-
p. 1365 - 1380
(2007/10/02)
-
- DERIVATIVES OF UNSATURATED AROMATIC ALCOHOLS IN PROPOLIS AND STYRAX BENZOIN
-
The benzoate of trans-coniferyl alcohol and the benzoate of trans-p-coumaryl alcohol have been obtained from propolis and the styrax benzoin, this being the first time that the latter has been described.
- Popravko, S. A.,Sokolov, I. V.,Torgov, I. V.
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p. 140 - 147
(2007/10/02)
-
- Photosensitized (Electron-Transfer) Rearrangements of Cinnamyl Alcohol Derivatives
-
Specific electron-donor compounds are capable of photosensitizing the rearrangement and solvolysis of several cinnamyl alcohol derivatives.Under suitable conditions, the formation of rearranged α-phenylallyl derivatives occurs in synthetically useful yields.The intermediates in this process have ionic character and have been trapped by methanol as methyl ether derivatives.The ability of the photosensitizers to effect these electron-transfer-initiated reactions correlates well with the enthalpy of reaction calculated by the Weller equation.
- Lee, George A.,Israel, Samuel H.
-
p. 4557 - 4563
(2007/10/02)
-