- Stereoselective synthesis of (+)-boronolide
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An efficient enantio- and stereocontrolled total synthesis of (+)-boronolide from valeraldehyde is described. The key steps include a Sharpless asymmetric dihydroxylation, a chelation controlled Grignard reaction followed by Sharpless asymmetric epoxidati
- Naidu, S. Vasudeva,Gupta, Priti,Kumar, Pradeep
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- STEREOSELECTIVE SYNTHESIS OF (E)-β-ALKYL ACRYLATES AND ACRYLAMIDES
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β-Tosyl-α,β-unsaturated esters and amides react regio and stereoselectively with carbanionic reagents to afford β-alkyl, alkenyl, or alkynyl substituted α,β-enoates or enamides with an E configuration.
- Najera, Carmen,Yus, Miguel
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- Enantio- and diastereocontrolled total synthesis of (+)-boronolide
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An efficient stereoselective total synthesis of (+)-boronolide from valeraldehyde is described. The key steps include a Sharpless asymmetric hydroxylation, a chelation-controlled vinyl Grignard reaction followed by a Sharpless asymmetric epoxidation, hydr
- Kumar, Pradeep,Naidu, S. Vasudeva
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- Copper-Catalyzed Azide–Ynamide Cyclization to Generate α-Imino Copper Carbenes: Divergent and Enantioselective Access to Polycyclic N-Heterocycles
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Here an efficient copper-catalyzed cascade cyclization of azide-ynamides via α-imino copper carbene intermediates is reported, representing the first generation of α-imino copper carbenes from alkynes. This protocol enables the practical and divergent synthesis of an array of polycyclic N-heterocycles in generally good to excellent yields with broad substrate scope and excellent diastereoselectivities. Moreover, an asymmetric azide–ynamide cyclization has been achieved with high enantioselectivities (up to 98:2 e.r.) by employing BOX-Cu complexes as chiral catalysts. Thus, this protocol constitutes the first example of an asymmetric azide–alkyne cyclization. The proposed mechanistic rationale for this cascade cyclization is further supported by theoretical calculations.
- Chen, Yang-Bo,Deng, Chao,Liu, Rai-Shung,Liu, Xin,Luo, Chen,Wang, Ze-Shu,Ye, Long-Wu,Zhai, Tong-Yi,Zhang, Yi-Ping
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supporting information
p. 17984 - 17990
(2020/08/21)
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- Visible-Light Promoted Distereodivergent Intramolecular Oxyamidation of Alkenes
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The visible-light-promoted diastereodivergent intramolecular oxyamination of alkenes is described to construct oxazolindinones, pyrrolidinones and imidazolidones via mild generation of primary amidyl radicals from functionalized hydroxylamines. A unique phenomenon of highly diastereoselective ring-opening of aziridines controlled by electron sacrifices was observed. Highly diastereoselective amino alcohols derivatives were obtained efficiently through this protocol in gram scales. The mechanistic studies suggested the isolatable anti-aziridine intermediates were generated quickly from primary amidyl radicals and the diastereoselectivities were controlled by pKavalues of the electron sacrifices.
- Ren, Xiang,Guo, Qihang,Chen, Jianhui,Xie, Hujun,Xu, Qing,Lu, Zhan
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supporting information
p. 18695 - 18699
(2016/12/26)
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- Total synthesis of umuravumbolide
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A simple and efficient stereoselective total synthesis of (+)-umuravumbolide (1b) and (-)-deacetylumuravumbolide (1a) starting from commercially available pentanal is described. The synthesis involves Sharpless asymmetric epoxidation, Jacobsen's hydrolytic kinetic resolution (HKR), and the Yamaguchi oxirane opening as key steps (Scheme2).
- Shekhar, Vanam,Reddy, Dorigondla Kumar,Venkateswarlu, Yenamandra
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p. 1593 - 1599
(2012/11/13)
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- A two-step ball milling method synthesizes and purifies α,β-unsaturated esters
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Over the last decade, solvent-free methods have been gaining interest as replacements for traditional organic chemistry techniques. While solvent-free methods are well known for many processes, a simple, solvent-free purification procedure that supplements them does not exist. We report the solvent-free synthesis of α,β-unsaturated esters using a solvent-free Horner-Wadsworth-Emmons (HWE) reaction using high-speed ball milling (HSBM). We were able to perform the HWE reaction on a variety of aldehydes, and isolate their respective a,b-unsaturated esters in high yields, purities, and diastereoselectivities. The Royal Society of Chemistry.
- Shearouse, William C.,Korte, Chelsea M.,Mack, James
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experimental part
p. 598 - 601
(2011/05/08)
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- Towards the catalytic formation of α,β-vinylesters and alkoxy substituted γ-lactones
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A facile, one pot, high yield synthesis of α,β-vinylester (1-14) and alkoxy substituted γ-lactones (15-28) has been achieved by the photochemical reaction of terminal acetylene (ferrocenyl phenyl trimethylsillyl, hexyl and cyclohexyl) with alcohol (methanol, ethanol and isopropanol) and carbon monoxide in presence of iron pentacarbonyl as a catalyst. The selectivity of the compounds depends on the time of photolysis of the reaction as well as the solvent used. A stable reaction intermediate ferrole was isolated, and further photolysis with alcohols, resulted in the formation of α,β-vinylester. All the compounds were fully characterised by spectroscopic methods and the molecular structures of compounds 1, 16, 17 and 20 were established crystallographically.
- Mathur, Pradeep,Joshi, Raj Kumar,Jha, Badrinath,Singh, Amrendra K.,Mobin, Shaikh M.
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experimental part
p. 2687 - 2694
(2010/11/21)
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- Catalytic synthesis of (E)-a,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene
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A practical and high yielding synthesis of a,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene was developed.
- Manzano, Ruben,Ozores, Lidia,List, Benjamin,Job, Andreas,Rodefeld, Lars
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experimental part
(2010/04/22)
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- A facile chemoenzymatic approach to chiral non-racemic β-alkyl-γ-amino acids and 2-alkylsuccinic acids. A concise synthesis of (S)-(+)-Pregabalin
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Both enantiomerically pure antipodes of GABA analogues were prepared as hydrochloride salts, by enzymatic kinetic resolution of their precursors ethyl 2-(nitromethyl)alkanoates. These latter compounds can be easily transformed into enantiomerically pure 2-alkylsuccinic acids by a Nef reaction followed by oxidation. Interestingly, this reaction was particularly easy for the neopentyl derivative (S)-(+)-7d, which underwent conversion into its corresponding succinic acid derivative (S)-(-)-8d in buffered solution. The absolute configurations of the main compounds of interest involved are given, together with their CD spectra.
- Felluga, Fulvia,Pitacco, Giuliana,Valentin, Ennio,Venneri, Cesare Daniele
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p. 945 - 955
(2008/09/21)
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- Virtually complete E-selective α,β-unsaturated ester synthesis by Hg(OTf)2-catalyzed hydration of sec-ethoxyalkynyl acetate
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The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded α,β-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction.
- Nishizawa, Mugio,Hirakawa, Hiroko,Nakagawa, Yuki,Yamamoto, Hirofumi,Namba, Kosuke,Imagawa, Hiroshi
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p. 5577 - 5580
(2008/09/17)
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- METHOD FOR THE PRODUCTION OF OLEFINS FROM CARBONYL COMPOUNDS
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A method for the production of a,?-unsaturated compounds of general formula (I) is disclosed, where R1 and R2 independently = H, substituted or unsubstituted alkyl or aryl, R3 = H, substituted or unsubstituted alkyl or aryl, or a functional group such as OR4, NR5R6, SR7, where R4, R5, R6 and R7 = common substituents in particular, alkyl- and/or aryl groups, or halogen, EWG = an electron withdrawing group such as for example, CO2H, CO2R8, CONR9R10, COSR11, CN, NO2, SO2R12, CHO, COR13, etc. where R8, R9, R10, R11, R12 and R13 = common substituents, in particular, alkyl- and/or aryl groups, in which a carbonyl compound of formula (II), in which R1 and R2 are as defined above, is reacted with a carboxylic acid of formula (III) in the presence of an amine or with the same acid generated in situ by the addition of an acid to the salt thereof in which R3 and EWG are as defined above. Under mild reaction conditions unsaturated esters with high (E)-stereoselectivity are obtained. The reaction typically occurs at room temperature or lower without particular requirements such as inert gas, exclusion of humidity, heat etc. CO2 and water are obtained as the only by-products.
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Page/Page column 5; 8
(2008/06/13)
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- Diastereoselective synthesis of α,β-unsaturated systems
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Functionalized Z-vinylic tellurides were used in substitution reactions with lower order cyanocuprates leading to α,β-unsaturated ketones and esters in good yields. In the case of acyclic tellurides, the product was obtained in high diastereoselectivity. The control of the stereoselectivity was achieved by simple change of the reaction temperature.
- Castelani, Priscila,Comasseto, Jo?o V.
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p. 2319 - 2326
(2007/10/03)
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- Practical synthesis of (E)-α,β-unsaturated esters from aldehydes
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Based on a modification of the Doebner-Knoevenagel reaction, a practical and highly efficient synthesis of β,β-unsaturated esters with excellent regio- and stereoselectivity was developed. The reactions are catalyzed by 4-dimethylaminopyridine in DMF at room temperature or below. Both aliphatic and aromatic aldehydes can readily be used in the process.
- List, Benjamin,Doehring, Arno,Hechavarria Fonseca, Maria T.,Wobser, Kathrin,Van Thienen, Hendrik,Torres, Ramon Rios,Galilea, Pedro Llamas
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p. 1558 - 1560
(2007/10/03)
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- Nitroalkanes and ethyl glyoxalate as common precursors for the preparation of both β-keto esters and α,β-unsaturated esters
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β-Nitro acrylic esters, obtained by the reaction of nitroalkanes and ethyl glyoxalate, are the key building blocks for the immediate synthesis of both the title compounds. In fact, their treatment with titanium trichloride produce the direct conversion to the β-keto esters, while their reaction with sodium boron hydride gives the one-pot synthesis of α,β- unsaturated esters through formal substitution of the vinylic nitro group with an hydrogen.
- Ballini, Roberto,Fiorini, Dennis,Palmieri, Alessandro
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p. 7027 - 7029
(2007/10/03)
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- Solvent-free Wittig olefination with stabilized phosphoranes - Scope and limitations
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Neat mixtures of arene/hetarenecarbaldehydes, alkanals as well as alkenals with alkyl (triphenylphosphoranylidene)acetates react exothermally to furnish the corresponding alkenes. In certain cases, heating has to be provided externally. Reaction times are short and yields are generally very high. Neat mixtures of ketones and alkyl (triphenylphosphoranylidene)acetates react preferentially under microwave irradiation. The better stabilized phosphoranes do not react in the solid state with aldehydes or ketones under conventional heating, but necessitate microwave irradiation, although not all of the phosphoranes have been found to be stable under microwave irradiation at 500 W (2450 MHz).
- Thiemann, Thies,Watanabe, Masataka,Tanaka, Yasuko,Mataka, Shuntaro
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p. 578 - 584
(2007/10/03)
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- Domino primary alcohol oxidation-wittig reaction: Total synthesis of ABT-418 and (E)-4-oxonon-2-enoic acid
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Domino oxidation of primary alcohols to α,β-unsaturated compounds using the combination of PCC-NaOAc and stabilized Wittig reagent and its application towards total synthesis of ABT-418 and 4-oxonon-2-enoic acid is described.
- Shet, Jyoti,Desai, Vidya,Tilve, Santosh
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p. 1859 - 1863
(2007/10/03)
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- Palladium-catalyzed reaction between aryl or alkenyl halides and (1-carbalkoxy-1-alkenyl)zinc iodides. A new class of unmasked β-substituted acrylate α-anion equivalents
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Unmasked β-substituted acrylate α-anion equivalents have been directly and very efficiently prepared by insertion of zinc metal into the carbon-iodine bonds of alkyl (E)- or (Z)-2-iodo-2-alkenoates, (E)- or (Z)-(4), respectively.The stereoisomeric composi
- Rossi, Renzo,Carpita, Adriano,Bellina, Fabio,Cossi, Paolo
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- A convenient synthesis of aziridine-2-carboxylic esters
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Optically active oxirane-2-carboxylic esters, prepared from allylic alcohols employing the Sharpless epoxidation, were treated with sodium azide.The azido alcohols obtained were subsequently converted into aziridine-2-carboxylic esters by reaction with triphenylphosphine, in good yields and with high optical purity.Various racemic oxirane-2-carboxylic esters were subjected to the same sequence of reactions.
- Legters, Johan,Thijs, Lambertus,Zwanenburg, Binne
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- NEW PREPARATION OF α,β-UNSATURATED ESTERS FROM 1-ALKENES VIA TWO CARBON HOMOLOGATION ROUTE. SYNTHESIS OF QUEEN SUBSTANCE
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2-Methylthio-4-alkenoic esters prepared from 1-alkenes and ethyl methylsulfinylacetate are converted into α,β-unsaturated esters via hydrogenation, oxidation, and thermolysis.This method was applied to the synthesis of queen substance.
- Ishibashi, Hiroyuki,Ohnishi, Minako,Senda, Toshihiko,Ikeda, Masazumi
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p. 857 - 864
(2007/10/02)
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- Methods for the introduction of a Phenylselenium Dichloride Group into he α-position of Carbonyl Compounds. Syntheses of Enones.
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Phenylselenium trichloride, PhSeCl3, direcly introduced, in fair yield, a PhSeCl2 group into the α-position of ketones with loss of HCl.To some extent, depending on the substrate, this reagent was also shown to act as a chlorinating agent toward ketones, yielding α-chloro ketones and α-phenylselenenyl ketones.The latter compounds were readily converted to selenium(IV) dichlorides by SO2Cl2 chlorination to significantly improve the overall yields of the selenetion process.The consecutive treatment of ketones with PhSeCl and SO2Cl2 could also be used for the introduction of a PhSeCl2 group, but this procedure was usually less efficient than the PhSeCl3-based one.Unsymmetrical ketones were selenated with poor regiocontrol.Aldehydes were primarily chlorinated by treatment with PhSeCl3, but consecutive treatment with PhSeCl3 and SO2Cl2 introduced a PhSeCl2 group into the α-position.Carboxylic acids and esters were ureactive toward PhSeCl3 and PhSeCl.PhSeCl3 underwent addition reactions with enones to introduce a PhSeCl2 group α or β to the carbonyl group, depending on the substrate.The carbonyl compounds substituted in the α-position with a PhSeCl2 group were easily converted to the corresponding α,β-unsaturated carbonyl compounds after hydrolysis/selenoxide elimination.Since the selenium(IV) intermediates involved were highly crustalline and easy to purify, the preparation of enones from symmetrical ketones via PhSeCl2 introduction/hydrolytic elimination was especially convenient to perform from the operational point of view.
- Engman Lars
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p. 4031 - 4037
(2007/10/02)
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- Mechanism of Formation of α,β-Unsaturated Esters in the Reaction of Ethyl Mercaptoacetate Dianion with Carbonyl Compounds
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Dianion derived fron ethyl mercaptoacetate undergoes aldol type reaction with a carbonyl compounds to give an adduct, which exhibited low diastereoselectivity.However, the adducts obtained by the reaction with a variety of aldehydes were subsequently treated with ethyl chloroformate in the presence of trivalent phosphorus compound to give (E)-isomers of α,β-unsaturated esters in high yields with greater than 85percent stereoselectivity regardless of the stereochemistry of the diastereomers of the adducts.The stereochemical mechanism and application of this reaction were studied in detail.
- Matsui, Syuichi
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p. 426 - 434
(2007/10/02)
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