- Nickel-Catalyzed Arylation of C(sp3)-O Bonds in Allylic Alkyl Ethers with Organoboron Compounds
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A nickel-catalyzed cross-coupling of allylic alkyl ethers with organoboron compounds through the cleavage of the inert C(sp3)-O(alkyl) bonds is described. Several types of allylic alkyl ethers can be coupled with various boronic acids or their derivatives to give the corresponding products in good to excellent yields with wide functional group tolerance and excellent regioselectivity. The gram-scale reaction and late-stage modification of biologically active compounds further prove the practicality of this synthetic method.
- Li, Xiaowei,Li, Yuxiu,Zhang, Zhong,Shi, Xiaolin,Liu, Ruihua,Wang, Zemin,Li, Xiangqian,Shi, Dayong
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supporting information
p. 6612 - 6616
(2021/09/02)
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- Efficient hydroarylation of terminal alkynes with sodium tetraphenylborate performed in water under mild conditions
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The hydroarylation of terminal alkynes with sodium tetraphenylborate was performed in high yield within 3 h at room temperature in water, using palladium(II) complexes with imidazole ligands as catalysts. Under these conditions, differently substituted phenylacetylene substrates were converted to arylalkenes and aryl-substituted dienes. High conversion and excellent selectivity were achieved in the hydroarylation of alkynols with sodium tetraphenylborate. Only one product, arylalkene with an OH group, was formed in these reactions with the yield dependent on the kind of alkynol used. A plausible hydroarylation reaction mechanism was proposed on the basis of the palladium species identified in the reaction mixture and H/D exchange studies. The contribution of water as the hydride source was evidenced.
- Koci?cka,Trzeciak
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- Synthesis and evaluation of 1,1,7,7-tetramethyl-9-azajulolidine (TMAJ) as a highly active derivative of N,N-dimethylaminopyridine
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1,1,7,7-Tetramethyl-9-azajulolidine (TMAJ), which theoretical studies have suggested as a highly active DMAP analog, was synthesized for the first time. The catalytic activity of TMAJ was confirmed by the acetylation reactions of various tert-alcohols. TMAJ showed much higher catalytic activity than DMAP and one of the highest activity levels among the conventional DMAP analogs. These experimental results were in good agreement with the previous theoretical studies.
- Tsutsumi, Tomohiro,Saitoh, Arisa,Kasai, Tomoyo,Chu, MengYue,Karanjit, Sangita,Nakayama, Atsushi,Namba, Kosuke
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supporting information
(2020/05/28)
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- Nickel-Catalyzed Stereodivergent Synthesis of E- and Z-Alkenes by Hydrogenation of Alkynes
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A convenient protocol for stereodivergent hydrogenation of alkynes to E- and Z-alkenes by using nickel catalysts was developed. Simple Ni(NO3)2?6 H2O as a catalyst precursor formed active nanoparticles, which were effective for the semihydrogenation of several alkynes with high selectivity for the Z-alkene (Z/E>99:1). Upon addition of specific multidentate ligands (triphos, tetraphos), the resulting molecular catalysts were highly selective for the E-alkene products (E/Z>99:1). Mechanistic studies revealed that the Z-alkene-selective catalyst was heterogeneous whereas the E-alkene-selective catalyst was homogeneous. In the latter case, the alkyne was first hydrogenated to a Z-alkene, which was subsequently isomerized to the E-alkene. This proposal was supported by density functional theory calculations. This synthetic methodology was shown to be generally applicable in >40 examples and scalable to multigram-scale experiments.
- Murugesan, Kathiravan,Bheeter, Charles Beromeo,Linnebank, Pim R.,Spannenberg, Anke,Reek, Joost N. H.,Jagadeesh, Rajenahally V.,Beller, Matthias
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p. 3363 - 3369
(2019/06/28)
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- Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
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Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
- Zhao, Chuan-Qi,Chen, Yue-Gang,Qiu, Hui,Wei, Lei,Fang, Ping,Mei, Tian-Sheng
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supporting information
p. 1412 - 1416
(2019/03/07)
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- Selective Aerobic Oxygenation of Tertiary Allylic Alcohols with Molecular Oxygen
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Aerobic epoxidation of tertiary allylic alcohols remains a significant challenge. Reported here is an efficient and highly chemoselective copper-catalyzed epoxidation and semipinacol rearrangement reaction of tertiary allylic alcohols with molecular oxygen. The solvent 1,4-dioxane activates dioxygen, thereby precluding the addition of a sacrificial reductant.
- Zhu, Bencong,Shen, Tao,Huang, Xiaoqiang,Zhu, Yuchao,Song, Song,Jiao, Ning
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supporting information
p. 11028 - 11032
(2019/07/08)
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- Half-Sandwich Ruthenium Carbene Complexes Link trans-Hydrogenation and gem-Hydrogenation of Internal Alkynes
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The hydrogenation of internal alkynes with [Cp?Ru]-based catalysts is distinguished by an unorthodox stereochemical course in that E-alkenes are formed by trans-delivery of the two H atoms of H2. A combined experimental and computational study now provides a comprehensive mechanistic picture: a metallacyclopropene (??2-vinyl complex) is primarily formed, which either evolves into the E-alkene via a concerted process or reacts to give a half-sandwich ruthenium carbene; in this case, one of the C atoms of the starting alkyne is converted into a methylene group. This transformation represents a formal gem-hydrogenation of a ?€-bond, which has hardly any precedent. The barriers for trans-hydrogenation and gem-hydrogenation are similar: whereas DFT predicts a preference for trans-hydrogenation, CCSD(T) finds gem-hydrogenation slightly more facile. The carbene, once formed, will bind a second H2 molecule and evolve to the desired E-alkene, a positional alkene isomer or the corresponding alkane; this associative pathway explains why double bond isomerization and over-reduction compete with trans-hydrogenation. The computed scenario concurs with para-hydrogen-induced polarization transfer (PHIP) NMR data, which confirm direct trans-delivery of H2, the formation of carbene intermediates by gem-hydrogenation, and their evolution into product and side products alike. Propargylic aOR (R = H, Me) groups exert a strong directing and stabilizing effect, such that several carbene intermediates could be isolated and characterized by X-ray diffraction. The gathered information spurred significant preparative advances: specifically, highly selective trans-hydrogenations of propargylic alcohols are reported, which are compatible with many other reducible functional groups. Moreover, the ability to generate metal carbenes by gem-hydrogenation paved the way for noncanonical hydrogenative cyclopropanations, ring expansions, and cycloadditions.
- Guthertz, Alexandre,Leutzsch, Markus,Wolf, Lawrence M.,Gupta, Puneet,Rummelt, Stephan M.,Goddard, Richard,Farès, Christophe,Thiel, Walter,Fürstner, Alois
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supporting information
p. 3156 - 3169
(2018/03/08)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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supporting information
p. 3677 - 3686
(2018/06/04)
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- Silver-catalyzed decarboxylative C(sp2)-C(sp3) coupling reactions: Via a radical mechanism
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A silver catalyzed decarboxylative C(sp2)-C(sp3) coupling of vinylic carboxylic acids with alcohols, alkylbenzenes, cycloalkanes and cyclic ethers was developed by using DTBP as an oxidant. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields. The reaction also shows good stereoselectivity, and only trans-isomers are obtained. In addition, a radical pathway would be involved to facilitate this decarboxylative C(sp2)-C(sp3) coupling reaction.
- Fang, Zhongxue,Wei, Chenlong,Lin, Jing,Liu, Zhenhua,Wang, Wei,Xu, Chenshu,Wang, Xuemin,Wang, Yu
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supporting information
p. 9974 - 9978
(2017/12/26)
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- E-selective semi-hydrogenation of alkynes with dinuclear iridium complexes under atmospheric pressure of hydrogen
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Semi-hydrogenation of alkynes was catalyzed by halide-bridged dinuclear iridium complexes, yielding (E)-alkenes with high selectivity. Mechanistic studies conducted with monohydride dinuclear species, dihydride mononuclear species, and trihydride dinuclear species led us to propose a mechanism involving dual cycles.
- Higashida, Kosuke,Mashima, Kazushi
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supporting information
p. 866 - 868
(2016/08/13)
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- Ligand-Controlled Cobalt-Catalyzed Transfer Hydrogenation of Alkynes: Stereodivergent Synthesis of Z- and E-Alkenes
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Herein, we report a novel cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes to Z- and E-alkenes. Effective selectivity control is achieved based on a rational catalyst design. Moreover, this mild system allows for the transfer hydrogenation of alkynes bearing a wide range of functional groups in good yields using catalyst loadings as low as 0.2 mol %. The general applicability of this procedure is highlighted by the synthesis of more than 50 alkenes with good chemo- and stereoselectivity. A preliminary mechanistic study revealed that E-alkene product was generated via sequential alkyne hydrogenation to give Z-alkene intermediate, followed by a Z to E alkene isomerization process.
- Fu, Shaomin,Chen, Nan-Yu,Liu, Xufang,Shao, Zhihui,Luo, Shu-Ping,Liu, Qiang
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supporting information
p. 8588 - 8594
(2016/07/27)
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- Design and synthesis of the basic Cu-doped zeolite X catalyst with high activity in oxidative coupling reactions
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The decarboxylative coupling of cinnamic acids with alcohols and the oxidative coupling of alkenes with aldehydes are typical organic reactions. Considering the characteristics and mechanisms of the reactions, the Cu-doped zeolite-X catalyst (Cu-X) with Lewis basic sites was synthesized and used for the two reactions. Compared with Cu, Cu2O, and CuBr2 catalysts (4-21%), the Cu-X catalyst (99%) shows extraordinary high activity in the decarboxylative coupling of cinnamic acids with alcohols. In addition, the Cu-X catalyst presents excellent performance in the oxidative coupling of alkenes with aldehydes. The strong interaction between Cu+ and the zeolite framework benefits the transformation of Cu2+ and Cu+ in the redox process, enhancing the reaction activity. More importantly, the Lewis basic sites on the Cu-X catalyst could favor the adsorption of the cinnamic acid, resulting in electron-rich density in the C=C bond, and therefore greatly improving the reaction activity.
- Chen, Shengchun,Shao, Zhen,Fang, Zhongxue,Chen, Qun,Tang, Ting,Fu, Wenqian,Zhang, Lei,Tang, Tiandi
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- Copper-Catalyzed Alkenylation of Alcohols with β-Nitrostyrenes via a Radical Addition-Elimination Process
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A new method for the preparation of allylic alcohol derivatives has been developed via a radical mechanism using DTBP as the radical initiator promoted by copper salt. The C(sp3)-H bond in various alcohols, toluene derivatives, and alkanes were successfully converted into C-C bonds to yield the desired products in moderate to good yields.
- Guo, Sheng-Rong,Yuan, Yan-Qin
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supporting information
p. 1961 - 1968
(2015/09/01)
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- Platinum catalysed hydrosilylation of propargylic alcohols
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A facile and user-friendly protocol has been developed for the selective synthesis of E-vinyl silanes derived from propargylic alcohols using a PtCl 2/XPhos catalyst system. The reaction is generally high yielding and provides a single regioiso
- McAdam, Catherine A.,McLaughlin, Mark G.,Johnston, Adam J. S.,Chen, Jun,Walter, Magnus W.,Cook, Matthew J.
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p. 4488 - 4502
(2013/08/23)
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- Enantioselective epoxidation of tertiary allylic alcohols by chiral dihydroperoxides
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gem-Dihydroperoxides were successfully used for the enantioselective epoxidation of tertiary and primary allylic alcohols. Epoxides derived from tertiary alcohols were obtained in yields up to 71% with ee's up to 52%.
- Bunge, Alexander,Hamann, Hans-Jürgen,Dietz, Dennis,Liebscher, Jürgen
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supporting information
p. 2446 - 2450
(2013/03/14)
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- Solvent free hydrostannation and Stille reactions using ionic liquid supported organotin reagents
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Hydrostannation reactions were performed cleanly using ionic liquid supported organotin reagents. These green reducing agents were used both under free radical and palladium-catalyzed conditions. One of the new ionic liquid supported organotin reagents so
- Faye, Djibril,Vybornyi, Mykhailo,Boeda, Fabien,Legoupy, Stéphanie
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p. 5421 - 5425
(2013/06/27)
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- Stereoselective synthesis of 1,3-dienes from propargylic alcohols by LiAlH4/AlCl3
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Herein we report that LiAlH4/AlCl3 is a very efficient reagent for the reductive dehydration of aryl propargylic alcohols in tetrahydrofuran solvent at reflux to give 1,3-dienes with good yields and high E selection. The reaction con
- Cui, Dong-Mei,Zhu, Kai,Chen, Li,Qi, Lang-Jun,Zhang, Cheng-Zhu,Zheng, Chen
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p. 2380 - 2384
(2013/07/26)
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- PtCl2/XPhos: A highly efficient and readily available catalyst for the hydrosilylation of propargylic alcohols
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A highly regioselective hydrosilylation of propargylic alcohols has been developed using an in situ prepared PtCl2/XPhos catalyst system. The reaction is tolerant of many functional groups and exhibits excellent regio and geometric selectivity.
- McLaughlin, Mark G.,Cook, Matthew J.
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supporting information; experimental part
p. 11104 - 11106
(2011/11/07)
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- Catalytic enantioselective aziridoarylation of aryl cinnamyl ethers toward synthesis of trans-3-amino-4-arylchromans
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Catalytic enantioselective one-pot aziridoarylation reaction of aryl cinnamyl ethers has been demonstrated in detail. Combination of suitable copper catalyst and chiral bis-oxazoline ligand was found to be very efficient for asymmetric aziridination followed by intramolecular arylation (Friedel-Crafts) reaction to provide a general and direct method for the synthesis of trans-3-amino-4-arylchromans with high regio-, diastereo- (dr > 99:1), and enantioselectivity (up to 95% ee) with moderate yield. trans-3-Amino-4- arylchroman is an advanced intermediate for the synthesis of chromenoisoquinoline compounds such as doxanthrine, a potent and selective full agonist for the dopamine-D1 receptor.
- Hajra, Saumen,Sinha, Debarshi
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scheme or table
p. 7334 - 7340
(2011/11/06)
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- Highly regioselective control of 1,2-addition of organolithiums to α,β-unsaturated compounds promoted by lithium bromide in 2-methyltetrahydrofuran: A facile and eco-friendly access to allylic alcohols and amines
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Very high regioselective 1,2-addition of organolithiums to α,α-unsaturated carbonyl-like compounds (ketones, aldehydes, and imines) in the presence of LiBr was achieved by carrying out reactions in the sustainable solvent 2-methyltetrahydrofuran. Excellent yields (in isolated product) of allylic alcohols and allylic amines were recovered under a simple experimental procedure at 0 °C.
- Pace, Vittorio,Castoldi, Laura,Hoyos, Pilar,Sinisterra, José Vicente,Pregnolato, Massimo,Sánchez-Montero, Ma. José
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supporting information; experimental part
p. 2670 - 2675
(2011/04/23)
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- Metal-free, aerobic dioxygenation of alkenes using hydroxamic acids
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(Chemical equation presented) One dioxygenation please, hold the metal: In the presence of either oxygen or air as the sole oxidant and external oxygen atom source, a variety of unsaturated hydroxamic acids afford cyclic hydroxamates that are readily converted into 1,2-diols, with the potential for high levels of reaction stereocontrol.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; experimental part
p. 4491 - 4494
(2010/08/21)
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- Reactions of vinyltributylgermanes and aryl halides under Heck conditions
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We describe the palladium-mediated reaction of vinyltributylgermanes with aryl halides under Heck conditions. Depending on their degree of substitution, (E)-vinyltributylgermanes preferentially afford either the cine or Z-alkenyl coupled products in moder
- Torres, Nicole M.,Lavis, Jér?me M.,Maleczka Jr., Robert E.
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scheme or table
p. 4407 - 4410
(2009/10/26)
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- Free-radical-initiated coupling reaction of alcohols and alkynes: Not co but C-C bond formation
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This work demonstrates an efficient method to prepare allylic alcohols via direct C-C bond formation using electron-rich alkynes and aliphatic alcohols initiated by tert-butyl hydroperoxide.
- Liu, Zhong-Quan,Sun, Liang,Wang, Jian-Guo,Han, Jie,Zhao, Yan-Kai,Zhou, Bo
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supporting information; scheme or table
p. 1437 - 1439
(2009/09/07)
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- Regio- and diastereoselective conjugate addition of Grignard reagents to aryl substituted α,β-unsaturated carbonyl compounds derived from Oppolzer's sultam
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Asymmetric conjugate addition of Grignard reagents to aryl substituted α,β-unsaturated carbonyl compounds (1) has been achieved with great regioselectivity (>20:1) and good to excellent diastereoselectivity (de up to 98%). The nucleophilicity and stereospecific blockade of the Grignard reagents play a key role in controlling the regioselectivities and diastereoselectivities of the conjugate addition reaction.
- Cao, Xiufang,Liu, Fang,Lu, Wenchang,Chen, Gang,Yu, Guang-Ao,Liu, Sheng Hua
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p. 5629 - 5636
(2008/09/21)
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- Palladium-catalyzed Heck arylations of allyl alcohols in ionic liquids: Remarkable base effect on the selectivity
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Pd-catalyzed Heck arylation of allyl alcohols in tetraalkylammonium ionic liquids (ILs) can be made highly selective toward the formation of either aromatic carbonyl compounds or aromatic conjugated alcohols by carefully choosing both the IL and the base.
- Calo, Vincenzo,Nacci, Angelo,Monopoli, Antonio,Ferola, Valentina
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p. 2596 - 2601
(2007/10/03)
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- Arylation of allyl alcohols in organic and aqueous media catalyzed by oxime-derived palladacycles: Synthesis of β-arylated carbonyl compounds
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A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, β-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol%). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio- and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important β-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance β-lilial. γ-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either γ-arylated alcohols or (E)-1-arylisoprenes.
- Alacid, Emilio,Najera, Carmen
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p. 2572 - 2584
(2008/09/19)
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- HISTONE DEACETYLASE INHIBITORS
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Hormone refractory metastatic disease can be treated with an oxyamide-containing compound through the inhibition of HDAC1 or HDAC2.
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Page/Page column 15-16
(2008/06/13)
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- An efficient palladium-catalyzed Heck coupling of aryl chlorides with alkenes
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Catalyst system PdCl2(PCy3)2/Cs 2CO3 in dioxane was found to be the efficient catalyst system for Heck cross-coupling reactions of deactivated, neutral, and activated aryl chlorides with a variety of alkenes under mild conditions to afford selectively E-arylated alkenes in good to excellent yields.
- Yi, Chenyi,Hua, Ruimao
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p. 2573 - 2576
(2007/10/03)
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- Palladium/magnesium-lanthanum mixed oxide catalyst in the heck reaction
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A new, reusable palladium/magnesium-lanthanum mixed oxide catalyst has been found to exhibit unprecedented high catalytic activity and selectivity for the heterogeneous Heck cross-coupling reaction of aryl halides with alkenes. The nature of the aryl halides has a determinate effect on the reaction yield. The corresponding reactions of a wide range of activated and non-activated aryl bromides and chlorides furnished the arylated product with high E/Z isomer ratios even already at 80°C. The stereoselectivity depended on the nature of the olefins.
- Cwik, Agnieszka,Hell, Zoltan,Figueras, Francois
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p. 523 - 530
(2007/10/03)
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- Stille reactions catalytic in tin: A "Sn-F" route for intermolecular and intramolecular couplings
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(Chemical Equation Presented) Polymethylhydrosiloxane (PMHS) made hypercoordinate by KF(aq) allows Me3SnH to be recycled during a Pd(0)-catalyzed hydrostannation/Stille cascade. Starting with a variety of alkynes, in situ vinyltin formation is followed by Stille reaction with aryl, styryl, benzyl, or vinyl electrophiles present in the reaction mixture. Both inter- and intramolecular versions of the process are possible with tin loads of approximately 6 mol %. Regeneration of the organotin hydride is believed to proceed through a Me3SnF intermediate. Given the aggregated nature of organotin fluorides and the ability to use these organotins in substoichiometric quantities, the hazards and purification problems associated with the removal of organotin wastes from reaction mixtures are minimized.
- Gallagher, William P.,Maleczka Jr., Robert E.
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p. 841 - 846
(2007/10/03)
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- Facile and Chemo-selective Cleavages of Allyl Ethers Utilizing Tetrabutylammonium Sulfate Radical Species
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Allyl ethers containing various functional groups reacted with tetrabutylammonium peroxydisulfate in acetonitrile under mild conditions to afford the corresponding cleaved alcohols in excellent yields.
- Yang, Seung Gak,Park, Min Young,Kim, Yong Hae
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p. 492 - 494
(2007/10/03)
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- Effect of InCl3 on the addition of Grignard reagents to α,β-unsaturated carbonyl compounds
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Control of 1,2- versus 1,4-addition of organometallic reagents to enones remains a long-standing problem. There is still no satisfactory 1,2-directing agent comparable to the 1,4-directing effect of copper salts. We report that the presence of just 5 mol% indium(III) chloride can significantly alter the amount of 1,2-product formed in these reactions.
- Kelly, Brian G.,Gilheany, Declan G.
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p. 887 - 890
(2007/10/03)
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- Histone deacetylase inhibitors
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Histone deacetylase is a metallo-enzyme with zinc at the active site. Compounds having a zinc-binding moiety, such as, for example, a carboxylic acid group, can inhibit histone deacetylase. Histone deacetylase inhibition can repress gene expression, inclu
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- Preparation of oxetanes by 4-endo trig electrophilic cyclisations of cinnamic alcohols
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The reaction of substituted cinnamic alcohols with bis(sym-collidine)bromine(I) hexafluorophosphate was examined. In general no oxetane was obtained when a substituent was fixed on the carbon-carbon double bond. However, oxetanes were formed in high yield
- Albert, Sébastien,Robin, Sylvie,Rousseau, Gérard
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p. 2477 - 2479
(2007/10/03)
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- Vilsmeier-Haack reaction of tertiary alcohols: Formation of functionalised pyridines and naphthyridines
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Vilsmeier-Haack reaction of 2-arylpropan-2-ols proceeds with multiple iminoalkylations leading to the formation of conjugated iminium salts which on ammonium acetate-induced cyclisation afford 4-arylnicotinaldehydes in good yields. Tertiary alcohols derived from aliphatic or alicyclic ketones by the addition of methyl Grignard are converted into substituted pyridines and naphthyridines by the action of Vilsmeier's reagent in N,N-dimethylformamide followed by nucleophile-assisted cyclisation in the presence of ammonium acetate.
- Thomas,Asokan
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p. 2583 - 2587
(2007/10/03)
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- Microwave-assisted one-pot hydrostannylation/Stille couplings.
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In a fraction of the time required by conventional methods, microwave-accelerated one-pot hydrostannylation/Stille coupling allows 1-alkynes to be efficiently transformed into 1,3-dienes or styrenes.
- Maleczka Jr.,Lavis,Clark,Gallagher
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p. 3655 - 3658
(2007/10/03)
-
- Mechanism of the Grignard Adddition Reaction. XVI. Homolytic and Concerted Mechanisms in the Reaction of α,β-Unsatureted Carbonyl Compounds with Grignard Reagents
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Kinetic measurements have shown that the addition of Grignard reagents to α,β-unsaturated carbonyl compounds takes place either by a concerted mechanism or by a homolytic mechanism.Phenylmagnesium bromide, which is incapable of homolysis, reacts rapidly in a 1,4-fashion if an s-cis conformation exists between the C=C and the C=O bonds, but only 1,2-addition takes place if the conformation is s-trans.tert-Butylmagnesium bromide is unsuited to the concerted reaction, but 1,4-addition takes place via homolysis.Primary and secondary Grignard reagents, like phenyl, react rapidly in a concerted manner with s-cis substrates, but unlike phenyl, these Grignard reagents may, with s-trans substrates, produce some 1,4-adduct via the homolytic mechanism.
- Holm, Torkil
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p. 925 - 929
(2007/10/02)
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- On the Way to Chiral Copper(I) Arenethiolate Catalysts for the Enantioselective Conjugate Addition of Methyl Lithium and Methyl Magnesium Iodide to Benzylideneacetone
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Selective conjugate addition (0 percent enantiomeric excess (e.e)) of organoarenethiolatocuprates (from methyl lithium and 2-phenylthiolatocopper(I), CuSAr*) to benzylideneacetone (BA) is found up to a LiMe/CuSAr* ratio of 2/1
- Lambert, Francois,Knotter, D. Martin,Janssen, Maurits D.,Klaveren, Mayra van,Boersma, Jaap,Koten, Gerard van
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p. 1097 - 1100
(2007/10/02)
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- Amphiphilic Reactions by Means of Exceptionally Bulky Organoaluminum Reagents. Rational Approach for Obtaining Unusual Equatorial, Anti-Cram, and 1,4 Selectivity in Carbonyl Alkylation
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Exceptionally bulky, oxygenophilic organoaluminum reagents, methylaluminum bis(2,6-di-tert-4-alkylphenoxide) (MAD and MAT), have been successfully utilized for stereoselective activation of carbonyl moiety.Combination of MAD or MAT with carbon nucleophiles such as organolithiums or Grignard reagents generates a new amphiphilic reaction system in which the alkylation may be interpreted as the nucleophilic addition of a reactive organometallic compound to an electrophilically activated carbonyl substrate in order to account for the regio- and stereochemical consequences.In contrast to the ordinary alkylations, the amphilic alkylation disclosed herein would be categorized into the new, yet unexplored class of alkylation that exhibits high chemoselectivity to carbonyl compounds, and more significantly it allows excellent equatorial and anti-Cram selectivity in carbonyl alkylations, hitherto difficult by the existing methodologies.Further, unusual conjugate addition of organolithium reagents to α,β-unsaturated carbonyl compounds has been accomplished by using the amphiphilic reaction system.
- Maruoka, Keiji,Itoh, Takayuki,Sakurai, Minoru,Nonoshita, Katsumasa,Yamamoto, Hisashi
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p. 3588 - 3597
(2007/10/02)
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- UNUSUAL CONJUGATE ADDITION OF ORGANOLITHIUM REAGENT TO α,β-UNSATURATED KETONE
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The conjugate addition of organolithium reagent to α,β-unsaturated ketone has been accomplished with methylaluminum bis(2,6-di-tert-butyl-4-alkylphenoxide) (MAD and MAT).Here combination of alkyllithium and MAD (or MAT) constitutes an amphiphilic system that allows to exhibit unusual selectivity in the alkylation of enones with alkyllithium.
- Maruoka, Keiji,Nonoshita, Katsumasa,Yamamoto, Hisashi
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p. 5723 - 5726
(2007/10/02)
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- 1,4-Addition of Triorganozincates and Silyldiorganozincates to α,β-Unsaturated Ketones
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Lithium and magnesium triorganozincates, prepared by combination of ZnCl2(TMEDA) with 3 molar equivalents of RLi or RMgX, or from dialkylzinc and 1 molar equivalent of RLi or RMgX, react with 2-cyclohexen-1-one (1) under mild conditions to produce moderate to good yields of the 1,4-addition products 2.The approximate reactivity order obtained from the product distribution using unsymmetrical zincates is tBuCH2 tBu, Me Me2PhSi.The latter groups are transferred with good selectivity from mixed reagents derived from Me2Zn.This sequence differs strikingly from that exhibited by unsymmetrical cuprates which transfer neopentyl very easily, and also tert-butyl more easily than the corresponding zincates.The methylation with Me3ZnLi is catalyzed by cobalt complexes.Other enones (7-13) generally give poor yields, and the cobalt-catalyzed methylation of isophorone (3) is complicated by a Kharasch-type deconjugation.Mixed silyldialkylzincates, Me2PhSiZnR2Li, produce the β-silyl ketones from a variety of unhindered or moderately hindered enones in practically useful yields; one example of an α,β-unsaturated ester (12) is also included.
- Tueckmantel, Werner,Oshima, Koichiro,Nozaki, Hitosi
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p. 1581 - 1593
(2007/10/02)
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- A NOVEL SYNTHESIS OF EPOXIDES AND ALLYLIC ALCOHOLS FROM CARBONYL COMPOUNDS THROUGH α,β-EPOXY SULFOXIDES
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Treatment of α,β-epoxy sulfoxides, easily prepared from carbonyl compounds with 1 equivalent of n-butyllithium at -100 deg C gave the desulfinated epoxides in good yields.The similar α,β-epoxy sulfoxides having arylmethyl group at α-position, on treatment
- Satoh, Tsuyoshi,Kaneko, Youhei,Yamakawa, Koji
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p. 2379 - 2382
(2007/10/02)
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- Stereospecific Desulfinylation of α,β-Epoxy Sulfoxides with Butyllithium. A New Synthesis of Epoxides and Allylic Alcohols from Carbonyl Compounds
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Desulfinylation of α,β-epoxysulfoxides, easily prepared from carbonyl compounds and 1-chloroalkyl phenyl sulfoxide, with 1 equivalent of butyllithium at low temperature gave epoxides in good yields.The similar α,β-epoxy sulfoxides having an arylmethyl gro
- Satoh, Tsuyoshi,Kaneko, Youhei,Yamakawa, Koji
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p. 2463 - 2470
(2007/10/02)
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- The Autoxidation of 1-Phenylalk-1-ynes. Proof of Oxirenes as Intermediates in the Oxidation of Acetylenes
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In the autoxidations of 1-phenylprop-1-yne, 1-phenylbut-1-yne, and 1-phenyl-3-methylbut-1-yne a considerable attack at the CC triple bond takes place.Both products of the oxidative cleavage of the CC bond and products formed through the corresponding oxirenes were detected.The oxirenes rearrange via the isomeric ketocarbenes to ketenes, which yield the corresponding carboxylic acids or their esters.A part of the intermediate ketenes is oxidized with decarboxylation to lower ketones.All products were identified and quantitatively determined after LiAlH4 reduction to the corresponding alcohols.
- Dao, Le Thi Anh,Blau, Karla,Pritzkow, Wilhelm,Schmidt-Renner, Wolfgang,Voerckel, Volkmar,Willecke, Lothar
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- Process for the preparation of aryl substituted aldehydes, ketones and alcohols
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Upon reacting an alcohol having an olefinic double bond with an aryl bromide or iodide in the presence of a Paladium catalyst, there is provided either an aryl substituted aldehyde, ketone or olefinic alcohol.
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