- Copper-Photocatalyzed Contra-Thermodynamic Isomerization of Polarized Alkenes
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The contra-thermodynamic isomerization of α- and β-substituted cinnamate derivatives catalyzed by the Cu(OAc)2/rac-BINAP complex under blue light irradiation is reported. The use of an oxazolidinone template, which favored the complexation of the copper catalyst to the substrate, allowed the E → Z isomerization of the catalytically formed chromophore under simple and robust reaction conditions in good to excellent ratios. The mechanism of this process based on the transient formation of a chromophore was also studied.
- Bouillon, Jean-Philippe,Brégent, Thibaud,Poisson, Thomas
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supporting information
p. 7688 - 7693
(2020/10/09)
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- Asymmetric Nazarov Cyclizations of Unactivated Dienones by Hydrogen-Bond-Donor/Lewis Acid Co–Catalyzed, Enantioselective Proton-Transfer
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We report an enantioselective Nazarov cyclization catalyzed by chiral hydrogen-bond-donors in concert with silyl Lewis acids. The developed transformation provides access to tri-substituted cyclopentenones in high levels of enantioselectivity (up to 95% e.e.) from a variety of simple unactivated dienones. Kinetic and mechanistic studies are consistent with a reversible 4π-electrocyclization C?C bond-forming step followed by rate- and enantio-determining proton-transfer as the mode of catalysis. (Figure presented.).
- Metternich, Jan B.,Reiterer, Martin,Jacobsen, Eric N.
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supporting information
p. 4092 - 4097
(2020/09/01)
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- Synthesis of α,β-Disubstituted Acrylates via Galat Reaction
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Galat reactions between aldehydes and substituted malonic acids half oxyester were found to be efficiently catalyzed by morpholine in refluxing toluene. This transformation allows the stereoselective synthesis of diverse α,β-disubstituted acrylates in moderate to good yields. This method constitutes an attractive alternative to existing methods in terms of scope and eco-compatibility.
- Xavier, Tania,Condon, Sylvie,Pichon, Christophe,Le Gall, Erwan,Presset, Marc
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supporting information
p. 6135 - 6139
(2019/08/28)
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- Macrolide Synthesis through Intramolecular Oxidative Cross-Coupling of Alkenes
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A RhIII-catalyzed intramolecular oxidative cross-coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo- and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3-conjugated diene structure.
- Jiang, Bing,Zhao, Meng,Li, Shu-Sen,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 555 - 559
(2018/02/21)
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- Control of Chemo-, Regio-, and Enantioselectivity in Copper Hydride Reductions of Morita-Baylis-Hillman Adducts
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Nonracemically ligated copper hydride can be used to effect tandem SN2′/1,2-reductions of racemic Morita-Baylis-Hillman (MBH) acetates to access enantioenriched chiral allylic alcohols with defined olefin geometry. MBH esters, including those w
- Linstadt, Roscoe T. H.,Peterson, Carl. A.,Jette, Carina I.,Boskovic, Zarko V.,Lipshutz, Bruce H.
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supporting information
p. 328 - 331
(2017/04/21)
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- Stereo- and chemoselective cross-coupling between two electron-deficient acrylates: An efficient route to (Z, E)-muconate derivatives
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A Ru-catalyzed direct oxidative cross-coupling reaction of acrylates was developed. It offers a straightforward and atom-economical protocol for the synthesis of functionalized (Z,E)-muconate derivatives in moderate to good yields with good stereo- and chemoselectivities. The conjugated muconates bearing differentiable terminal functionality can be selectively transformed into versatile synthetic intermediates widely used in organic synthesis.
- Hu, Xu-Hong,Zhang, Jian,Yang, Xiao-Fei,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 3169 - 3172
(2015/03/30)
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- Polyethyleneimine-Supported Triphenylphosphine and Its Use as a Highly Loaded Bifunctional Polymeric Reagent in Chromatography-Free One-Pot Wittig Reactions
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A polyethyleneimine-supported triphenylphosphine reagent has been synthesized and used as a highly loaded bifunctional homogeneous reagent in a range of one-pot Wittig reactions that afforded high yields of the desired products after simple purification procedures. The approach also served efficiently in tandem reaction sequences involving a one-pot Wittig reaction followed by conjugate reduction of the newly formed alkene product in situ. In these transformations, the phosphine oxide groups generated in the Wittig reaction served as the catalyst for activating trichlorosilane in the subsequent reduction reaction.
- Xia, Xuanshu,Toy, Patrick H.
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supporting information
p. 1737 - 1743
(2015/07/20)
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- Highly enantioselective hydrogenation of 2-substituted-2-alkenols catalysed by a ChenPhos-Rh complex
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Highly enantioselective hydrogenation of a variety of 2-substituted-2- alkenols has been achieved using a ChenPhos-Rh complex as catalyst, giving ≥99% ee for most substrates. Optically active antifungal agent amorolfine was first synthesised using hydrogenation as the key step. This journal is
- Wang, Quanjun,Liu, Xueying,Liu, Xian,Li, Bin,Nie, Huifang,Zhang, Shengyong,Chen, Weiping
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supporting information
p. 978 - 980
(2014/01/06)
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- Arenediazonium salts immobilized in imidazolium ionic liquids as electrophilic partners in the Pd(OAc)2-catalyzed Matsuda-Heck arylation
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The utility of arenediazonium salts immobilized in imidazolium-ILs [BMIMPF6 and BMIMBF4] for facile, high yielding, synthesis of olefins via the Pd(OAc)2-catalyzed Matsuda-Heck arylation reaction has been demonstrated. The reaction can also be performed as a two-step process in the IL starting from ArNH2, by sequential in-situ diazotization-arylation. Simple product isolation and the recycling/re-use of the IL are additional advantages of this one-pot method.
- Kalkhambkar, Rajesh G.,Laali, Kenneth K.
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experimental part
p. 1733 - 1737
(2011/05/05)
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- A convenient synthesis of (E)-α,β-unsaturated esters with total stereoselectivity promoted by catalytic samarium diiodide
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Synthesis of (E)-α,β-unsaturated esters in high yields and with total stereoselectivity is achieved from α-halo-β-hydroxy esters promoted by catalytic amounts of SmI2. The starting compounds were easily prepared from α-halo esters and aldehydes as a mixture of stereoisomers. A mechanism is proposed to explain this samarium(II)-promoted catalytic β-elimination reaction. Georg Thieme Verlag Stuttgart.
- Concellón, José M.,Rodríguez-Solla, Humberto,Concellón, Carmen,Díaz-Pardo, Ainhoa,Llavona, Ricardo
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experimental part
p. 262 - 264
(2011/03/21)
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- Stereoselective olefination of N-sulfonyl imines with stabilized phosphonium ylides for the synthesis of electron-deficient alkenes
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An unprecedented protocol has been developed for thestereoselective synthesis of structurally diverse electron-deficient alkenes in moderate to excellent yields from readily accessible N-sulfonyl imines and stabilized phosphonium ylides. Significantly, the olefination reaction of N-sulfonylimines with nitrile-stabilized phosphonium ylides affords an array of α,β-unsaturated nitriles with high Z selectivity, and the reactions with ester-, amide-, and ketone-stabilized phosphonium ylides afford α,β-unsaturated esters, amides, and ketones with high E selectivity, respectively. Spectroscopic analysis of the reaction mixtures and trapping of the intermediates allow plausible mechanisms to be proposed. Initialimine/ylide addition leads to the formation of betaines that cyclize to form 1,2-azaphosphetanes that subsequently eliminate iminophosphoranes to yield alkenes. For the synthesis of electron-deficient 1,2-disubstituted alkenes, the presence of an electron-withdrawing group in the betaine allows rapid interconversion between its two diastereomers through proton transfer. The Z/E selectivity for alkene synthesis is determined by the different rates at which the two betaine diastereomers form the corresponding 1,2-azaphosphetane diastereomers. In contrast, the Z/E selectivity for the synthesis of electron-deficient trisubstituted alkenes originates from the diastereoselective addition of stabilized phosphonium ylides to N-sulfonyl imines.
- Fang, Fan,Li, Yuan,Tian, Shi-Kai
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experimental part
p. 1084 - 1091
(2011/04/15)
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- A novel catalytic decarbonylative Heck-type reaction and conjugate addition of aldehydes to unsaturated carbonyl compounds
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A novel rhodium-catalyzed decarbonylative reaction of aldehydes with unsaturated carbonyl compounds was discovered to generate Heck-type reaction product and conjugate addition product.
- Yang, Luo,Correia, Camille A.,Guo, Xiangyu,Li, Chao-Jun
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experimental part
p. 5486 - 5489
(2010/10/20)
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- Chemoenzymatic synthesis of (+)-α-polypodatetraene and methyl (5R,10R,13R)-labda-8-en-15-oate
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The reported enzymatic resolution products {acetate of (1S,4aS,8aS)-1,2,3, 4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2- ethylene acetal} (8aS)-5 (>99% ee)] and [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a- decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-4 (98% ee) were converted to (+)-α-polypodatetraene (1) and methyl (5R,10R,13R)-labda-8-en-15-oate (2), respectively. For the synthesis of (5R,10R,13R)-2, chiral isoprene congener (3S)-26 corresponding to the right part of 2 was synthesized based on the lipase-assisted resolution of (±)-2-methyl-3- (p-methoxyphenyl)propanol (17).
- Kinoshita, Masako,Miyake, Takahiro,Arima, Yuusuke,Oguma, Minako,Akita, Hiroyuki
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p. 118 - 123
(2008/09/17)
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- An efficient synthesis of (E)-α,β-unsaturated ketones and esters with total stereoselectivity by using chromium dichloride
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(E)-α,β-Unsaturated ketones 1 or esters 2 can be obtained with complete stereoselectivity by reaction of different 2-chloro-3-hydroxy ketones 3 or esters 4 and CrCl2. A comparative study of the results of synthesis of ketones 1 with CrCl2 or samarium is performed. A mechanism to explain both β-elimination reactions has been proposed.
- Concellón, José M.,Rodríguez-Solla, Humberto,Méjica, Carmen
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p. 3292 - 3300
(2007/10/03)
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- Synthesis of (E)-α,β-unsaturated esters with total diastereoselectivity by using chromium dichloride
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Synthesis of di- and trisubstituted (E)-α,β-unsaturated esters is easily achieved by using chromium dichloride through an elimination reaction of a diastereoisomeric mixture of α-halo-β-hydroxy esters. The starting materials were easily prepared by the aldol reaction of lithium enolates of α-chloroesters with aldehydes. A mechanism to explain this elimination process is proposed.
- Concellón, José M.,Rodríguez-Solla, Humberto,Méjica, Carmen
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p. 2977 - 2979
(2007/10/03)
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- Synthesis of (E)-α,β-unsaturated esters and (Z)-vinyl halides with total or high diastereoselectivity by using samarium metal
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A highly diastereoselective β-elimination of 2-halo-3-hydroxy esters 1 or O-acetylated 1,1-dihaloalkan-2-ols 4 is achieved with samarium in the presence of diiodomethane, yielding α,β-unsaturated esters 2 or vinyl halides 5, respectively. The β-elimination reaction was promoted by samarium diiodide, which was generated in situ. The starting halohydrins 1 or 4 are easily prepared by reaction of the corresponding lithium enolates of α-halo esters or dihalomethyllithium with aldehydes at -78°C. The influence of the reaction conditions and the structure of the starting compounds on the diastereoselectivity of the β-elimination reactions is discussed, A comparative study of the β-elimination reaction with preformed SmI2 and metallic samarium is also performed. These elimination reactions can be explained by the proposed mechanism. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
- Concellon, Jose M.,Rodriguez-Solla, Humberto,Huerta, Monica,Perez-Andres, Juan A.
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p. 1839 - 1847
(2007/10/03)
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- Synthesis of (E)-α,β-unsaturated esters with total or high diastereoselectivity from α,β-epoxyesters
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Chemical equation presented High stereoselective β-elimination in 2,3-epoxyesters 1 was achieved using samarium diiodide, yielding α,β-unsaturated esters 2, in which the C=C bond is di-, tri- or tetrasubstituted. The starting compounds 1 are easily prepared by reaction of the corresponding lithium enolates of a-chloroesters with aldehydes or ketones at -78 °C. The influence of the reaction conditions and the structure of the starting compounds in the stereoselectivity of the β-elimination reaction is also discussed.
- Concellon, Jose M.,Bardales, Eva
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p. 189 - 191
(2007/10/03)
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- Sequential elimination-reduction reactions promoted by samarium diiodide: Synthesis of 2,3-dideuterioesters or -amides
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A facile and general sequential elimination/reduction process promoted by samarium diiodide provides an efficient method for synthesizing saturated esters or amides 3 from readily available starting materials. The reaction involves a β-elimination of the starting 2-halo-3-hydroxyesters or -amides 1 and subsequent 1,4-reduction of the obtained α,β-unsaturated esters or amides in the presence of H2O. When D2O is used instead of H2O, 2,3-dideuterioesters or -amides 4 are isolated. A mechanism is proposed to account for this synthesis.
- Concellon, Jose M.,Rodriguez-Solla, Humberto
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p. 4266 - 4271
(2007/10/03)
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- A simple method for the synthesis of 2-amino-1(4′-methoxyphenyl)-propane
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Synthesis of 2-amino-1-(4′-methoxyphenyl)-propane (II) starting from p-anisaldehyde (1) in 67% overall yield is described. Key reactions involved Horner-Wadswoth-Emmons olefination of 1 to form the ester 2 and Hoffmann degradation of amide 5 to obtain the amine II.
- Mereyala,Koduru
-
p. 3005 - 3010
(2007/10/03)
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- Kinetic study of microwave-assisted Wittig reaction of stabilised ylides with aromatic aldehydes
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The Wittig reaction of a pool of stabilised ylides and aromatic aldehydes was carried out in a microwave oven. Only a few minutes were needed for high conversion rates under microwave heating in comparison to hour time with traditional methods.
- Frattini, Sara,Quai, Monica,Cereda, Enzo
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p. 6827 - 6829
(2007/10/03)
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- Synthesis of (E)-a,β-unsaturated esters and amides with total selectivity using samarium diiodide
-
β-elimination of α-halo-β-hydroxyesters 1 was achieved by using samarium diiodide as a metalating reagent, and afforded di- and trisubstituted (E)-α,βunsaturated esters 2 with total steroselectivity. This method has also been extended to the corresponding disubstituted (E)-α,β-unsaturated amides.
- Concellon, Jose M.,Perez-Andres, Juan A.,Rodriguez-Solla, Humberto
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p. 2773 - 2775
(2007/10/03)
-
- Acyclic Stereoselection in the Ortho Ester Claisen Rearrangement
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The ortho ester Claisen rearrangement of trisubstituted allylic alcohols exhibits significant levels of diastereoselection. In E allylic alcohols, a 1,3-diaxial interaction develops in the chairlike transition state leading to the anti isomer, rendering the reaction syn selective by a factor of 3-5 to 1. In Z allylic alcohols, the 1,3-diaxial interaction develops in the transition state leading to the syn isomer, generating an anti:syn selectivity of 6-15 to 1. The relative stereochemistry of the syn isomer was confirmed independently by the synthesis of the mycotoxin botryodiplodin.
- Daub, G. William,Edwards, James P.,Okada, Carol R.,Allen, Jana Westran,Maxey, Claudia Tata,Wells, Matthew S.,Goldstein, Alexandra S.,Dibley, Michael J.,Wang, Clarence J.,Ostercamp, Daniel P.,Chung, Steven,Cunningham, Paula Shanklin,Berliner, Martin A.
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p. 1976 - 1985
(2007/10/03)
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- Synthetic Study of tautomycin and Tautomycetin. Stereocontrolled Construction of the Dialkylmaleic Anhydride Segment
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Strategies for the synthesis of a dialkylmaleic anhydride segment of tautomycin and tautomycetin are presented.The most difficult point was the stereocontrolled construction of the tetrasubstituted olefin.The maleate-type olefin construction through dehyd
- Ueno, Tohru,Oikawa, Masato,Oikawa, Hideaki,Ichihara, Akitami
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p. 2104 - 2110
(2007/10/02)
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- Activated Alumina Promoted Stereoselective Wittig Reaction
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Aldehydes undergo efficient E-stereoselective Wittig olefination with alkylidenetriphenylphosphoranes in the presence of activated alumina under mild conditions with high yields.
- Dhavale, Dilip D.,Sindkhedkar, Milind D.,Mali, Raghao S.
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p. 414 - 415
(2007/10/03)
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- 1-alkoxycarbonylalkylidenetriphenylarsoranes: Preparation and reactions
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The higher homologues of the well-studied alkoxycarbonylmethylenetriphenylarsonium ylide (3, R=H) can be easily obtained through the sequence: a), preparation of alkyl 2-trifloxyalkanoates (1); b), reaction between these trifloxyderivatives and triphenylphosphine to give 1-alkoxycarbonylalkyltriphenylarsonium triflates (2); and c), basic treatment of the triphenylarsonium triflates (2) with alumina-supported potassium fluoride to give 1-alkoxycarbonylalkyledenetriphenylarsonium ylides (3). These higher homologues of (3, R=H) react with aromatic aldehydes in good to excellent yields, and give rise to synthetically interesting 'coupling' and cyclopropanation reactions.
- Castells,Lopez-Calahorra,Yu
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p. 13765 - 13774
(2007/10/02)
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- Carbanions phosphonate prepares par voie electrochimique: formation et reactivite vis-a-vis d'un aldehyde
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Reactivity towards p-methoxybenzaldehyde (ArCHO) of electrochemically generated phosphonate carbanions has been investigated.Electrolyses were carried out at a mercury cathode in DMF and two routes to the desired carbanion have been compared: (i) Deprotonation of phosphonates of general formula (EtO)2P(O)CHYW (Y = W = Cl; Y = H, W = Cl; Y = Cl, W = CO2Et; Y = H, W = CO2Et; Y = CH3, W = CO2Et; Y = Cl, W = CH3), by the bases resulting from the electroreduction of azobenzene; addition of the carbanion formed onto the carbonyl group takes place and leads to the adduct (EtO)2P(O)CYW(Ar)O-. (ii) Two-electron reduction of halophosphonates (EtO)2P(O)CXYW (X = Cl, Y and W as above; X = Br, W = CO2Et, Y = Cl, Br, or CH3); when no H atom is present on the carbon bearing the phosphonate group (Y and W no = H), the same evolution leading to the above adduct is observed, on the contrary, when Y = H, the electrogenerated carbanion deprotonates the substrate and the resulting carbanion (EtO)2P(O)CXW reacts with the aldehyde; giving the adduct (EtO)2P(O)CXW(Ar)O-.Evolution of the intermediate adduct depends on the substituents Y (or X) and W: when W = CO2Et, whatever the nature of Y (or X), diethyl phosphate is eliminated with formation of the ethylenic ArCH=CWY (or X) (Wittig-Horner reaction); the same evolution is observed when Y = W = Cl.When W = Cl and Y = H or CH3, the final product is the phosphonate epoxyde resulting from chloride elimination (Darzens reaction).Chemo- and stereoselectivity depend only on the nature of Y and W but are independent of the mode of generation of the carbanion.Yields are limited by side-protonation reactions, which are related to the basicity of the phosphonate carbanions.Analysis of the results permits selection of the optimal electrolysis conditions for purposes of synthesis.Key words: electrosynthesis, electrogenerated bases, phosphonates, Wittig-Horner.
- Le Menn, Jean-Christophe,Sarrazin, Jean,Tallec, Andre
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p. 1332 - 1343
(2007/10/02)
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- Qualitative investigation of the Wittig-Horner reaction by means of electrogenerated bases
-
Deprotonation reactions of various phosphonates by the basis issued from azobenzene electroreduction in DMF can be studied by cyclic voltammetry; a qualitative classification of the phosphonates according to their acidity can be established.The occurence of the Wittig-Horner reaction when an aldehyde is present can be followed by the same technique and, in some cases, the reactivity of the aldehydes can be classified.The results of preparative electrolyses performed in a standard procedure are in good agreement with the previous analytical data.
- Le Menn, J.C.,Sarrazin, J.
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p. 781 - 786
(2007/10/02)
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- Synthesis of 3-(4'-Methoxy-1'-phenyl)allyl Citronellyl Ether and Related Structures
-
Substituted aromatic allyl citronellyl ethers (1-4) have been prepared and structures supported by spectral data.The compounds were tested for juvenile hormone activity.
- Bhatia, M. S.,Rani, Poonam,Xavierkutty, M. C.,Lal, Jawahar
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p. 411 - 413
(2007/10/02)
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- Ethynylindenyl compounds and derivatives thereof used in the treatment of pain, fever and inflammation
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Novel ethynylindenyl compounds and derivatives are described. Their use in the treatment of inflammation is also disclosed.
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