- Kinetic resolution ofN-aryl β-amino alcoholsviaasymmetric aminations of anilines
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An efficient kinetic resolution ofN-aryl β-amino alcohols has been developedviaasymmetricpara-aminations of anilines with azodicarboxylates enabled by chiral phosphoric acid catalysis. Broad substrate scope and high kinetic resolution performances were afforded with this method. Control experiments supported the critical roles of the NH and OH group in these reactions.
- Guo, Zheng,Xie, Jinglei,Hu, Tao,Chen, Yunrong,Tao, Houchao,Yang, Xiaoyu
-
supporting information
p. 9394 - 9397
(2021/09/22)
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- Catalytic Intermolecular C(sp3)-H Amination: Selective Functionalization of Tertiary C-H Bonds vs Activated Benzylic C-H Bonds
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A catalytic intermolecular amination of nonactivated tertiary C(sp3)-H bonds (BDE of 96 kcal·mol-1) is reported for substrates displaying an activated benzylic site (BDE of 85 kcal·mol-1). The tertiary C(sp3)-H bond is selectively functionalized to afford α,α,α-Trisubstituted amides in high yields. This unusual site-selectivity results from the synergistic combination of Rh2(S-Tfpttl)4, a rhodium(II) complex with a well-defined catalytic pocket, with tert-butylphenol sulfamate (TBPhsNH2), which leads to a discriminating rhodium-bound nitrene species under mild oxidative conditions. This catalytic system is very robust, and the reaction was performed on a 50 mmol scale with only 0.01 mol % of catalyst. The TBPhs group can be removed under mild conditions to afford the corresponding NH-free amines.
- Brunard, Erwan,Boquet, Vincent,Van Elslande, Elsa,Saget, Tanguy,Dauban, Philippe
-
supporting information
p. 6407 - 6412
(2021/05/29)
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- Visible-light-mediated alkylation of 4-alkyl-1,4-dihydropyridines with alkenyl sulfones
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Herein we report a mild, general protocol for visible-light-mediated alkylation of 4-alkyl-1,4-dihydropyridines with alkenyl sulfones. The protocol permits efficient functionalization of sulfones with a broad range of cyclic and acyclic secondary and tert
- Dong, Jianyang,Liu, Yuxiu,Wang, Qingmin,Yue, Fuyang
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p. 8924 - 8928
(2021/11/04)
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- Enantio- and Regioselective NiH-Catalyzed Reductive Hydroarylation of Vinylarenes with Aryl Iodides
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A highly enantio- and regioselective hydroarylation process of vinylarenes with aryl halides has been developed using a NiH catalyst and a new chiral bis imidazoline ligand. A broad range of structurally diverse, enantioenriched 1,1-diarylalkanes, a structure found in a number of biologically active molecules, have been obtained with excellent yields and enantioselectivities under extremely mild conditions.
- He, Yuli,Liu, Chuang,Yu, Lei,Zhu, Shaolin
-
supporting information
p. 21530 - 21534
(2020/10/02)
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- Enzymatic Primary Amination of Benzylic and Allylic C(sp3)-H Bonds
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Aliphatic primary amines are prevalent in natural products, pharmaceuticals, and functional materials. While a plethora of processes are reported for their synthesis, methods that directly install a free amine group into C(sp3)-H bonds remain unprecedented. Here, we report a set of new-to-nature enzymes that catalyze the direct primary amination of C(sp3)-H bonds with excellent chemo-, regio-, and enantioselectivity, using a readily available hydroxylamine derivative as the nitrogen source. Directed evolution of genetically encoded cytochrome P411 enzymes (P450s whose Cys axial ligand to the heme iron has been replaced with Ser) generated variants that selectively functionalize benzylic and allylic C-H bonds, affording a broad scope of enantioenriched primary amines. This biocatalytic process is efficient and selective (up to 3930 TTN and 96percent ee), and can be performed on preparative scale.
- Jia, Zhi-Jun,Gao, Shilong,Arnold, Frances H.
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supporting information
p. 10279 - 10283
(2020/07/27)
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- Iron-Catalyzed Cross-Coupling of Alkynyl and Styrenyl Chlorides with Alkyl Grignard Reagents in Batch and Flow
-
Transition-metal-catalyzed cross-coupling chemistry can be regarded as one of the most powerful protocols to construct carbon–carbon bonds. While the field is still dominated by palladium catalysis, there is an increasing interest to develop protocols that utilize cheaper and more sustainable metal sources. Herein, we report a selective, practical, and fast iron-based cross-coupling reaction that enables the formation of Csp?Csp3 and Csp2?Csp3 bonds. In a telescoped flow process, the reaction can be combined with the Grignard reagent synthesis. Moreover, flow allows the use of a supporting ligand to be avoided without eroding the reaction selectivity.
- Deng, Yuchao,Wei, Xiao-Jing,Wang, Xiao,Sun, Yuhan,No?l, Timothy
-
supporting information
p. 14532 - 14535
(2019/11/21)
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- Stereospecific Iron-Catalyzed Carbon(sp2)-Carbon(sp3) Cross-Coupling with Alkyllithium and Alkenyl Iodides
-
An efficient synthetic protocol involving iron-catalyzed cross-coupling reactions between organolithium compounds and alkenyl iodides as key coupling partners was achieved. More than 30 examples were obtained with moderate to good yields and high stereospecificity. Gram-scale and synthetic applications of this procedure are recorded herein to demonstrate its feasibility and potential utilization.
- Lu, Xiao-Lin,Shannon, Mark,Peng, Xiao-Shui,Wong, Henry N. C.
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p. 2546 - 2549
(2019/03/26)
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- Fe-Catalyzed decarbonylative alkylation-peroxidation of alkenes with aliphatic aldehydes and hydroperoxide under mild conditions
-
A convenient Fe-catalyzed decarbonylative alkylation-peroxidation of alkenes with aliphatic aldehydes and TBHP to provide chain elongated peroxides is developed, which is further applied to the one-pot synthesis of alkylated ketones. Aliphatic aldehydes were decarbonylated into 1°, 2° and 3° alkyl radicals at low temperature which subsequently allows the cascade construction of C(sp3)-C(sp3) and C(sp3)-O bonds via radical insertion and radical-radical coupling. Various alkenes including mono-substituted, terminally disubstituted or internally disubstituted styrenes bearing synthetically useful functional groups and electron-poor acrylates were tolerated.
- Wu, Chuan-Shuo,Li, Rong,Wang, Qi-Qiang,Yang, Luo
-
supporting information
p. 269 - 274
(2019/01/28)
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- Nickel-Catalyzed Anionic Cross-Coupling Reaction of Lithium Sulfonimidoyl Alkylidene Carbenoids With Organolithiums
-
The mechanistic platform for a novel nickel0-catalyzed anionic cross-coupling reaction (ACCR) of lithium sulfonimidoyl alkylidene carbenoids (metalloalkenyl sulfoximines) with organometallic reagents is reported herein, affording substituted alkenylmetals and lithium sulfinamides. The Ni0-catalyzed ACCR of three different types of metalloalkenyl sulfoximines, including acyclic, axially chiral and exocyclic derivatives, with sp2 organolithiums and sp2 and sp3 Grignard reagents has been studied. The ACCR of metalloalkenyl sulfoximines with PhLi in the presence of the Ni0-catalyst and precatalyst Ni(PPh3)2Cl2 afforded alkenyllithiums, under inversion of configuration at the C atom and complete retention at the S atom. In a combination of experimental and DFT studies, we propose a catalytic cycle of the Ni0-catalyzed ACCR of lithioalkenyl sulfoximines. Computational studies reveal two distinctive pathways of the ACCR, depending on whether a phosphine or 1,5-cyclooctadiene (COD) is the ligand of the Ni atom. They rectify the underlying importance of forming the key Ni0-vinylidene intermediate through an indispensable electron-rich Ni0-center coordinated by phosphine ligands. Fundamentally, we present a mechanistic study in controlling the diastereoselectivity of the alkenyllithium formation via the key lithium sulfinamide coordinated Ni0-vinylidene complex, which consequently avoids an unselective formation of an alkylidene carbene Ni-complex and ultimately racemic alkenyllithium.
- Bülow, Gerd,Baik, Mu-Hyun,Decker, Jürgen,Erdelmeier, Irene,Gais, Hans-Joachim,Park, Steve,Won, Joonghee
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supporting information
(2020/02/28)
-
- Enantioselective, Lewis Base-Catalyzed, Intermolecular Sulfenoamination of Alkenes
-
A method for the catalytic, enantioselective, intermolecular, 1,2-sulfenoamination of alkenes is described. Functionalization is achieved through the intermediacy of an enantioenriched, configurationally stable thiiranium ion generated by Lewis base activation of a readily available sulfur electrophile. A diverse set of anilines and benzylamines react with different styrenes to afford products in good yield and stereoselectivity. Downstream manipulation of the products is facilitated by deprotonation of the amines to enable carbon-sulfur bond cleavage.
- Roth, Aaron,Denmark, Scott E.
-
supporting information
p. 13767 - 13771
(2019/09/10)
-
- RETRACTED ARTICLE: Copper-Catalyzed Decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) Coupling of Substituted Cinnamic Acids and 3-Phenyl Propiolic Acid with N-Tosyl Oxaziridines
-
A mild and efficient strategy for decarboxylative C(sp2)-C(sp3) and C(sp)-C(sp3) coupling of α,β-unsaturated carboxylic acids such as substituted cinnamic acids and 3-phenyl propiolic acid with N-Tosyl oxaziridines was developed. The corresponding products were achieved in moderate to good yields with excellent stereoselectivity. Base-free and oxidant-free conditions allow good functional group tolerance. Radical inhibitors such as TEMPO and BHT completely suppressed the reactions suggesting a radical mechanism was involved. This study is supposed to broaden the frontier of oxaziridines' chemistry and to open up a novel cascade for alkylating reagents.
- Nguyen, Bich-Ngoc,Cao, Hai-Thuong
-
supporting information
p. 5912 - 5915
(2019/08/07)
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- Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
-
We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
- Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
-
supporting information
p. 5723 - 5728
(2019/04/03)
-
- Iron-Catalyzed Vinylic C?H Alkylation with Alkyl Peroxides
-
A variety of alkyl peresters and alkyl diacyl peroxides, which are readily accessible from carboxylic acids, are utilized as general primary, secondary, and tertiary alkylating reagents for iron-catalyzed vinylic C?H alkylation of vinyl arenes, dienes, and 1,3-enynes. This transformation affords olefinic products in up to 98 % yield with high E/Z values. A broad range of functionalities, including carboxyl, boronic acid, methoxy, ester, amino, and halides, are tolerated. This protocol provides a facile approach to some olefins that are difficult to access, and hence, offers an alternative to existing systems. The synthetic utility of this method is demonstrated by late-stage functionalization of selected natural-product derivatives.
- Ge, Liang,Jian, Wujun,Zhou, Huan,Chen, Shaowei,Ye, Changqing,Yu, Fei,Qian, Bo,Li, Yajun,Bao, Hongli
-
supporting information
p. 2522 - 2528
(2018/08/01)
-
- Regioselective Rh-Catalyzed Hydroformylation of 1,1,3-Trisubstituted Allenes Using BisDiazaPhos Ligand
-
The efficient hydroformylation of 1,1,3-trisubstituted allenes is accomplished with low loadings of a Rh catalyst supported by a BisDiazaPhos (BDP) ligand. The ligand identity is key to achieving high regioselectivity, while the mild reaction conditions m
- Eshon, Josephine,Landis, Clark R.,Schomaker, Jennifer M.
-
p. 9270 - 9278
(2017/09/22)
-
- Umpolung Synthesis of 1,3-Amino Alcohols: Stereoselective Addition of 2-Azaallyl Anions to Epoxides
-
We report the direct preparation of 1,3-amino alcohols that contain up to three contiguous stereogenic centers by the umpolung coupling of imines and epoxides. Nucleophilic 2-azaallyl anions, generated from imines, are stereoselectively added to epoxides to furnish 1,3-amino alcohols after hydrolysis of the product imine. Transformations afford amino alcohols with >98% site selectivity with respect to both reaction partners and in up to >98% yield and >20:1 dr.
- Daniel, Paige E.,Weber, Alexandria E.,Malcolmson, Steven J.
-
supporting information
p. 3490 - 3493
(2017/07/15)
-
- Facile synthesis of Z -alkenes via uphill catalysis
-
Catalytic access to thermodynamically less stable Z-alkenes has recently received considerable attention. These approaches have relied upon kinetic control of the reaction to arrive at the thermodynamically less stable geometrical isomer. Herein, we present an orthogonal approach which proceeds via photochemically catalyzed isomerization of the thermodynamic E-alkene to the less stable Z-isomer which occurs via a photochemical pumping mechanism. We consider two potential mechanisms. Importantly, the reaction conditions are mild, tolerant, and operationally simple and will be easily implemented.
- Singh, Kamaljeet,Staig, Shannon J.,Weaver, Jimmie D.
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p. 5275 - 5278
(2014/05/06)
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- Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents
-
Palladium-catalysed cross-coupling of secondary C(sp3) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation with organolithium reagents, herein we present a Pd-catalysed cross-coupling of secondary alkyllithium reagents with aryl and alkenyl bromides. The reaction proceeds at room temperature and on short timescales with high selectivity and yields. This methodology is also applicable to hindered aryl bromides, which are a major challenge in the field of metal catalysed cross-coupling reactions.
- Vila, Carlos,Giannerini, Massimo,Hornillos, Valentin,Fananas-Mastral, Martin,Feringa, Ben L.
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p. 1361 - 1367
(2014/03/21)
-
- Investigations on the operation of stereochemical drift in the wittig reaction by NMR and variable-temperature NMR spectroscopy of oxaphosphetane intermediates and their quench products
-
Within the currently accepted mechanism of the Li-salt-free Wittig reaction, the phenomenon of stereochemical drift remains the one remaining "loose end" in an otherwise internally consistent explanation of a large body of diverse observations. The term describes the nonstereospecific decomposition of the oxaphosphetane (OPA) intermediate in reactions of certain alkylides with certain aldehydes. In this paper, it is shown that the previous examples in which drift occurs are not merely isolated aberrations from the observed norm, but rather that there is a general phenomenon in reactions of ethylides with benzaldehydes. Variable-temperature NMR (VTNMR) spectroscopy was used to establish that the amount and diastereomeric ratio of the OPA intermediates do not change below a certain temperature. At and above the temperature at which OPA decomposition to alkene and phosphine oxide begins to occur, the alkene shows a different diastereomeric ratio to the OPA, which indicates the occurrence of stereochemical drift. In one example, owing to an apparent remarkable coincidence of rates, the diastereomeric ratio of the OPA does not change above the decomposition temperature, even though stereochemical drift occurs in the formation of the alkene product. An alternative mechanism for drift involving its catalysis by aldehyde was not confirmed. Drift was also shown not to occur in similar Wittig reactions of structurally related longer-chain alkylides by stereospecific decomposition of OPA intermediates generated from β-hydroxyphosphonium salts (β-HPSs). The extremely useful (and generally applicable) NMR techniques, 1H-31P HMBC and selective 1H{31P}, which we have utilised to establish kinetic diastereomeric ratios, are described in full for the first time. Details of the determination of the relative stereochemistry of two β-HPSs (derived from acid quenching of OPAs) by X-ray crystallography are also given. Stereochemical drift, previously only identified in a handful of isolated examples, is confirmed by variable-temperature NMR (VTNMR) spectroscopy as a general phenomenon in Wittig reactions of phosphonium ethylides with aromatic aldehydes. However, reactions of structurally related longer-chain alkylides are irreversible. The NMR methods used are described in full. Copyright
- Byrne, Peter A.,Muldoon, Jimmy,Ortin, Yannick,Mueller-Bunz, Helge,Gilheany, Declan G.
-
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- Iron thiolate complexes: Efficient catalysts for coupling alkenyl halides with alkyl grignard reagents
-
Ironing out the kinks: Efficient new catalytic systems based on iron thiolates are described for the iron-catalyzed cross-coupling of alkyl Grignard reagents with alkenyl halides (see scheme). The reaction is highly chemo- and stereoselective. With this new procedure, the use of N-methylpyrrolidone as a co-solvent is no longer required. Copyright
- Cahiez, Gerard,Gager, Olivier,Buendia, Julien,Patinote, Cindy
-
supporting information; experimental part
p. 5860 - 5863
(2012/07/01)
-
- A convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions
-
A mild method for the facile removal of phosphine oxide from the crude products of Wittig and Appel reactions is described. Work-up with oxalyl chloride to generate insoluble chlorophosphonium salt (CPS) yields phosphorus-free products for a wide variety of these reactions. The CPS product can be further converted into phosphine.
- Byrne, Peter A.,Rajendran, Kamalraj V.,Muldoon, Jimmy,Gilheany, Declan G.
-
p. 3531 - 3537
(2012/05/20)
-
- Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium
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The synthetic protocol for the reduction of alcohols to hydrocarbons by using hydriodic acid, first described by Kiliani more than 140 years ago, was improved to be more applicable to organic synthesis. Instead of a strongly acidic, aqueous solution, a biphasic toluene-water reaction medium was used, which allowed the conversion of primary, secondary and tertiary benzylic alcohols, in good yields and short reaction times, into the corresponding hydrocarbons. Red phosphorous was used as the stoichiometric reducing agent. Keto, ester, amide or ether groups are tolerated, and catalytic amounts of hydriodic acid (0.2 equiv) in the presence of 0.6 equiv phosphorous are sufficient to achieve conversion.
- Dobmeier, Michael,Herrmann, Josef M.,Lenoir, Dieter,Koenig, Burkhard
-
supporting information; experimental part
p. 330 - 336
(2012/05/20)
-
- Iron-catalysed, hydride-mediated reductive cross-coupling of vinyl halides and Grignard reagents
-
An iron-catalysed, hydride-mediated reductive cross-coupling reaction has been developed for the preparation of alkanes. Using a bench-stable iron(ii) pre-catalyst, reductive cross-coupling of vinyl iodides, bromides and chlorides with aryl- and alkyl Grignard reagents successfully gave the products of formal sp3-sp3 cross-coupling reactions.
- Le Bailly, Bryden A. F.,Greenhalgh, Mark D.,Thomas, Stephen P.
-
supporting information; experimental part
p. 1580 - 1582
(2012/03/26)
-
- Unequivocal experimental evidence for a unified lithium salt-free wittig reaction mechanism for all phosphonium ylide types: Reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products
-
The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
- Byrne, Peter A.,Gilheany, Declan G.
-
supporting information; experimental part
p. 9225 - 9239
(2012/07/14)
-
- Cu(I)-catalyzed, α-selective, allylic alkylation reactions between phosphorothioate esters and organomagnesium reagents
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Regiocontrol of allylic alkylation reactions involving hard nucleophiles remains a significant challenge and continues to be an active area of research. The lack of general methods in which α-alkylation is favored underscores the need for the development of new processes for achieving this type of selectivity. We report that Cu(I) catalyzes the allylic substitution of phosphorothioate esters with excellent α-regioselectivity, regardless of the nature of the Grignard reagent that is used. To the best of our knowledge, the Cu-catalyzed allylic alkylation of phosphorothioate esters has never been described. We have also developed a simple protocol for inducing high α selectivity starting from secondary allylic halides. This is accomplished by using sodium phosphorothioates as an additive.
- Lauer, Andrew M.,Mahmud, Farzeen,Wu, Jimmy
-
p. 9119 - 9123
(2011/08/04)
-
- Practical and stereoselective synthesis of β-amino sulfones from alkyl phenyl sulfones and N-(tert-butylsulfinyl) aldimines
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A practical and straightforward approach for the highly stereoselective synthesis of β-amino sulfones was developed. With lithium bis(trimethylsilyl)amide as the base, the corresponding sulfone-stabilized carbanion derived from alkylphenyl sulfone can be
- Zhang, Hua,Li, Ya,Xu, Wei,Zheng, Wenrui,Zhou, Pei,Sun, Zhihua
-
supporting information; experimental part
p. 6502 - 6505
(2011/11/05)
-
- SmI2-Mediated 3-exo-trig Cyclization of β,γ- unsaturated carbonyl compounds: Diastereoselective synthesis of cyclopropanols
-
SmI2-mediated 3-exo-trig cyclizations of β,γ- unsaturated carbonyl compounds to generate cyclopropanols are not generally observed processes. The reported examples are limited to β,γ- unsaturated carbonyl compounds that possess ester groups con
- Martin-Fontecha, Mar,Agarrabeitia, Antonia R.,Ortiz, Maria J.,Armesto, Diego
-
supporting information; experimental part
p. 4082 - 4085
(2010/11/04)
-
- A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N -Sulfonyl imines
-
The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
- Dong, De-Jun,Li, Hai-Hua,Tian, Shi-Kai
-
supporting information; experimental part
p. 5018 - 5020
(2010/06/13)
-
- Generation of ortho-quinone methides by p-TsOH on silica and their hetero-Diels-Alder reactions with styrenes
-
(Chemical Equation Presented) 2-Arylchromans were readily prepared from the hetero-Diels-Alder reactions of styrenes with the ortho-quinone methides (o-QMs) which, in turn, were generated by treating the MOM-protected benzylacetate derivatives with p-TsOH immobilized on silica (PTS-Si) in toluene under mild conditions (0°C to rt). The corresponding chromans were obtained in moderate to excellent yields (42-97%) and in moderate to excellent diastereoselectivity (up to >99:1).
- Batsomboon, Paratchata,Phakhodee, Wong,Ruchirawat, Somsak,Ploypradith, Poonsakdi
-
supporting information; experimental part
p. 4009 - 4012
(2009/10/14)
-
- Lithium hydroxide as base in the Wittig reaction. A simple method for olefin synthesis
-
A mild and practical procedure for the Wittig olefination, promoted by lithium hydroxide and triphenylbenzyl phosphonium bromide, has been set up for the synthesis of stilbenes and styrenes. The experimental conditions allow aromatic, heteroaromatic, unsaturated and saturated aliphatic aldehydes to give final products in good yields.
- Antonioletti,Bonadies,Ciammaichella,Viglianti
-
p. 4644 - 4648
(2008/09/20)
-
- Nickel-catalyzed cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with alkyl grignard reagents using (Z)-3,3-dimethyl-1,2- bis(diphenylphosphino)but-1-ene as ligand
-
A combination of nickel(II) acetylacetonate and (Z)-3,3-dimethyl-1,2- bis(diphenylphosphino)but-1-ene catalyzes cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with alkyl Grignard reagents. Not only primary but also secondary alkyl Grignard reagents can be employed. Georg Thieme Verlag Stuttgart.
- Kanemura, Shigenari,Kondoh, Azusa,Yorimitsu, Hideki,Oshima, Koichiro
-
scheme or table
p. 2659 - 2664
(2009/04/05)
-
- Stereoselectivity of the Wittig reaction in two-phase system
-
The Wittig reaction of benzyltriphenylphosphonium chloride with aliphatic and aromatic aldehydes has been investigated, respectively, in two-phase solvent system (dichloromethane / water) in the presence of sodium hydroxide. Both, the effect of the size of aliphatic aldehydes and the effect of substitution on benzaldehyde to the cis/trans ratios have been studied. It has been found that the use of aliphatic aldehydes in Wittig reaction gives higher ratio of trans alkene isomer. However, when aromatic aldehyde is used, the ratio of the cis alkene isomer is found to be higher than that of the trans isomer. In addition, the electronic nature of substituents (electron-donating group versus electron-withdrawing group) causes some changes in the cis/trans ratio of the product stilbene.
- Al Busafi, Saleh,Al Rawahi, Waffa
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p. 370 - 374
(2008/02/10)
-
- 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.
-
p. 1953 - 1969
(2007/10/03)
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- A simple radical addition - Elimination route to geometrically pure (E)-alkene and chromanone derivatives via β-nitrostyrene
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Various geometrically pure (E)-β-alkyl-styrenes have been synthesized by the radical NO2 substitution of alkyl moieties generated via hydrogen abstraction followed by decarbonylation from aliphatic aldehydes. These reactions, which involve a high chemical selectivity and regioselectivity constitute a new route to (E)-β-alkylstyrenes. Both aliphatic and aromatic aldehydes can be used in this novel reaction. When 2-allyloxybenzaldehyde was used, the benzoyl radical added directly to the double bond without decarbonylation to give the 3-cinnamylchroman-4-one. This unique difference between aliphatic and aromatic aldehydes represents a simple route for the synthesis of biologically important chromanones.
- Jang, Yeong-Jiunn,Yan, Ming-Chung,Lin, Yung-Feng,Yao, Ching-Fa
-
p. 3961 - 3963
(2007/10/03)
-
- Polystyrene-supported benzyl selenide: An efficient reagent for highly stereocontrolled synthesis of olefins and allylic alcohols
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Polystyrene-supported benzyl selenide has been prepared. This novel reagent was treated with LDA to produce a selenium-stabilized carbanion, which reacted with alkyl halide and epoxides, followed by selenoxide syn-elimination, to give olefins and allylic alcohols, respectively.
- Huang, Xian,Xu, Weiming
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p. 5495 - 5497
(2007/10/03)
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- Synthesis of epoxides from aldehydes and tosylhydrazone salts catalysed by triphenylarsine: Complete trans selectivity for all combinations of coupling partners
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Triphenylarsine catalyses the formation of epoxides from carbonyl compounds and tosylhydrazone salts. This convergent synthesis gives complete trans selectivity for all aldehyde and tosylhydrazone salt coupling partners.
- Aggarwal, Varinder K.,Patel, Mamta,Studley, John
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p. 1514 - 1515
(2007/10/03)
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- Novel synthesis of alkenes via triethylaluminum-induced free radical reactions of alkyl iodides and β-nitrostyrenes
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Reactions of (E)-β-nitrostyrenes 1 with triethylaluminum (Et3Al) 2 and alkyl iodide (RI) 3, 4, or 5 in the presence of benzoyl peroxide in diethyl ether solution at room temperature to give 60-100% of the different (E)-alkenes 6, 7, or 8. Under
- Liu, Jing-Yuan,Liu, Ju-Tsung,Yao, Ching-Fa
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p. 3613 - 3615
(2007/10/03)
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- Novel synthesis of alkenes via triethylborane-induced free-radical reactions of alkyl iodides and β-nitrostyrenes
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Reactions of (E)-β-nitrostyrenes 1 and triethylborane 2 or tricyclohexylborane 4 in THF solution at room temperature in the presence of oxygen in the air as radical initiator generate high yields of trans-alkenes (E)-3 or (E)-5. Medium to high yields of d
- Liu,Jang,Shih,Hu,Chu,Yao
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p. 6021 - 6028
(2007/10/03)
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- Reaction of tribenzylphosphine oxide with aldehydes
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Tribenzylphosphine oxide readily and stereoselectively reacts with aliphatic, aromatic, and heteroaromatic aldehydes in the presence of strong bases yielding exclusively (or predominantly) E-isomers of 1-organyl-2-phenylethenes and dibenzylphosphinic acid
- Gusarova,Ivanova,Reutskaya,Arbuzova,Baikalova,Deryagina,Russavskaya,Trofimov
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p. 1726 - 1730
(2007/10/03)
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- The synthesis of carboxylic acids via an aldol-grob reaction sequence
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Ketones react with aromatic aldehydes via a tandem Aldol-Grob reaction sequence. The reaction, initiated by boron trifluoride, produces a carboxylic acid fragment and can serve as an alternative to the Baeyer-Villiger reaction.
- Kabalka,Li,Tejedor,Malladi,Gao,Trotman
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p. 2783 - 2787
(2007/10/03)
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- Highly stereo and chemoselective iron-catalyzed alkenylation of organomagnesium compounds
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In the presence of Fe(acac)3, Grignard reagents react readily with alkenyl halides (X = I, Br or Cl) in a THF/NMP mixture to give the cross-coupling products in high yields with an excellent stereoselectivity (≤99.5%). The scope of the reaction is very broad since a vast array of functional groups are tolerated (esters, nitriles, aromatic or aliphatic halides and even ketones). The procedure reported herein is an interesting alternative to the classical Pd- or Ni-catalyzed reactions, especially for preparative organic chemistry.
- Cahiez, Gerard,Avedissian, Hovsep
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p. 1199 - 1205
(2007/10/03)
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- Conjugative interaction in styrenes
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Conjugative interactions of the carbon-carbon double bond are fundamental in organic chemistry. In this work, equilibria are established among conjugated and unconjugated isomers of two β-substituted styrenes, 1-phenylbut-1-ene and 1-phenyl-3-methylbut-1-ene, and one α,β-disubstituted styrene, 2-phenyl-5-methylhex-2-ene, over a range of temperatures (the van't Hoff method) in hexamethylphosphoric triamide and potassium tert-butoxide. From the trans styrenes of the first two sets, an enthalpy of conjugative interaction of phenyl vis-a-vis alkyl (ΔΔH(ConjInter/Alk)) = -2.5 ± 0.2 kcal/mol [-5.1 kcal/mol defined as phenyl vis-a-vis hydrogen (ΔΔH(ConjInter/H))] is observed, while the cis styrenes reveal an attenuated ΔΔH(ConjInter/Alk) of -1.1 kcal/mol (ΔΔH(ConjInter/H)) = -2.7 kcal/ mol). The α-methyl group in the third set also leads to a reduced conjugative interaction. Entropy plays an important role in determining positions of equilibrium. Free energies of conjugation are reported for several sterically hindered o-methyl-substituted styrenes.
- Von Doering,Benkhoff, Johannes,Carleton, Peter Smart,Pagnotta, Marco
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p. 10947 - 10955
(2007/10/03)
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- Tellurium-zinc exchange reaction. A new preparative method of alkenylzinc reagents
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Alkenyl tellurides were converted to the corresponding alkenylzinc compounds by the reaction with diethylzinc. The exchange reaction proceeds efficiently in THF at room temperature with retention of the stereochemistry of the starting tellurides. The successive reaction of the formed alkenylzinc with 4-iodotoluene in the presence of Pd(PPh3)4 afforded a cross-coupling product as a single stereoisomer.
- Terao, Jun,Kambe, Nobuaki,Sonoda, Noboru
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p. 4741 - 4744
(2007/10/03)
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- A new generation of 'instant ylids': Powder mixtures of phosphonium salts and potassium hydride as storable precursors to Wittig reagents
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Mixing a finely pulverized alkyltriphenylphosphonium salt and potassium hydride in 1:1 molar ratio gives a ready-to-use powder the components of which react rapidly when tert-butyl methyl ether is added under stirring. When, in general after a few minutes, the generation of the (triphenylphosphonio)alkanide is complete, it can be immediately used for the Wittig olefination of a carbonyl compound. Compared to sodium amide based 'instant ylids', the new blends offer little advantage as long as simple phosphonium salts are ingredients but they extend considerably the shelf life of mixtures containing heterosubstituted derivatives such as methylthiomethyl- or picolyltriphenylphosphonium salts. Copyright (C) 1996 Elsevier Science Ltd.
- El-Khoury, Mirella,Wang, Qian,Schlosser, Manfred
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p. 9047 - 9048
(2007/10/03)
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- The Stereochemistry of Rearrangements of Aryl and Hetaryl Groups to Primary Carbenic Centers
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The products and stereochemistries of carbenic decompositions of varied 2-aryl-1-diazoalkanes and 1-diazo-2-(2-hetaryl)propanes have been determined.
- Slack, W. E.,Taylor, W.,Moseley, C. G.,Chang, K. T.,Kraska, A.,et al.
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p. 2647 - 2650
(2007/10/02)
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- Cyclocondensation of oxalyl chloride with 1,2-glycols
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Oxalyl chloride reacts with a wide range of acyclic 1,2-glycols 1 in the presence of triethylamine to produce 1,3-dioxolan-2-ones 3 together with 1,4-dioxane-2,3-diones 2. Ethylene glycol (1d), monosubstituted ethylene glycols 1e, j-l, and erythro-1,2-disubstituted ethylene glycols 1f, m, o provide the cyclic carbonates 3 as the minor products, while the threo-compounds 1g, i, n, p, q and pinacol (1h) afford 3 as the main products. The formation of 3 may be rationalized in terms of stereoelectronically controlled cleavage of the conjugate base 17- of the tetrahedral intermediates. The rate of the conformational change of 17- into 18- and the equilibrium constant between these conformers are proposed to be the major factors affecting the reaction pattern.
- Iida,Itaya
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p. 10511 - 10530
(2007/10/02)
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- Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
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The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
- Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
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p. 856 - 878
(2007/10/02)
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- STEREOSELECTIVITY OF THE WITTIG-HORNER REACTION WITH BENZYLPHOSPHONATE CARBANIONS AND ALDEHYDES
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The interaction of Li-diethylbenzylphosphonate 1-Li with aldehydes 2 is studied at different reaction conditions, the corresponding β-hydroxyethanephosphonate 3 being isolated.It is found that in these cases the aldol stage of the HWE reaction is not stereoselective or threo isomers predominate.The elimination stage leads only to trans-alkene due to the electron and steric influence of the substituents at the phosphorus atom. Key words: Stereoselectivity; benzylphosphonate carbanion; reaction with aldehydes; threo/erythro ratio; 2-hydroxyphosphonates.
- Petrova, Jordanka,Momchilova, Snejana,Vassilev, Nikolay G.
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- X-ray structural analysis and thermal decomposition of 1-Aza-2-silacyclobutanes: A new route to silanimine species
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X-ray structural analysis of a 1-aza-2-silacyclobutane derivative, trans-1-(tert-butyldimethylsilyl)-2,2,4-triphenyl-3-isopropyl-1-aza-2- silacyclobutane (1), has been carried out for the first time. The 1-aza-2-silacyclobutane skeleton is of small angle strain, being nonplanar in relation to the nearly planar nitrogen atom, and has normal bond lengths, aside from the considerably long C-N bond. 1-Aza-2-silacyclobutanes undergo thermal decomposition around 200 °C in toluene to form a silanimine species, R2S=NR, and an olefin. The formation of silanimine has been confirmed by quantitative formation of the dimer and a 1:1 adduct with Me3SiOEt in the copyrolysis. The 3,4-trans and -cis isomers form trans and cis olefins, respectively. The decomposition rates obey the first-order rate law and decrease in the order 3,4-trans > 3,4-cis > 3,3,4-trisubstituted derivatives. The results are analyzed by the concerted [2s + 2a] cycloreversion mechanisms.
- Tamao, Kobei,Nakagawa, Yoshiki,Ito, Yoshihiko
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p. 218 - 221
(2007/10/02)
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