- Synthesis of S-(+)-4-methyl-3-heptanone, the principal alarm pheromone of Atta texana, and its enantiomer
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The principal alarm pheromone of Atta texana S-(+)-4-methyl-3-heptanone, and its enantiomer have been prepared synthetically in high optical purity.
- Riley,Silverstein
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Read Online
- Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?
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A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland–Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the rearrangements. Furthermore, these organocatalysts slowed down the Ireland–Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving hydrogen-donating organocatalysts and kinetic experiments suggest that the catalysts bind stronger to the starting silyl ketene acetals than to transition structures thus leading to inefficient rearrangement reactions.
- Kri?tofíková, Dominika,Filo, Juraj,Me?iarová, Mária,?ebesta, Radovan
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- Copper(II)-Catalyzed Alkene Aminosulfonylation with Sodium Sulfinates for the Synthesis of Sulfonylated Pyrrolidones
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A copper-catalyzed direct aminosulfonylation of unactivated alkenes with sodium sulfinates for the efficient synthesis of sulfonylated pyrrolidones is described. This reaction features good functional group tolerance and wide substrate scope, providing an efficient and straightforward protocol to access this kind of pyrrolidones. Moreover, preliminary mechanistic investigations disclosed that a free-radical pathway might be invovled in the process.
- Rao, Wei-Hao,Jiang, Li-Li,Liu, Xiao-Meng,Chen, Mei-Jun,Chen, Fang-Yuan,Jiang, Xin,Zhao, Jin-Xiao,Zou, Guo-Dong,Zhou, Yu-Qiang,Tang, Lin
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supporting information
p. 2890 - 2893
(2019/04/30)
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- Synthesis of 5-[(Pentafluorosulfanyl)methyl]-γ-butyrolactones via a Silver-Promoted Intramolecular Cyclization Reaction
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The synthesis of 5-[(pentafluorosulfanyl)methyl]-γ-butyrolactones bearing different substituents at position 3 or 4 is reported. A silver-promoted intramolecular cyclization of substituted 4-chloro-5-(pentafluorosulfanyl)pentanoic acids allows the preparation of the substituted SF5-containing γ-butyrolactones in up to 96 % yield.
- Roudias, Majdouline,Gilbert, Audrey,Paquin, Jean-Fran?ois
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p. 6655 - 6665
(2019/11/03)
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- Synthesis of Enantiomerically Enriched 2-Hydroxymethylalkanoic Acids by Oxidative Desymmetrisation of Achiral 1,3-Diols Mediated by Acetobacter aceti
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The stereoselective desymmetrisation of achiral 2-alkyl-1,3-diols is performed by oxidation of one of the two enantiotopic primary alcohol moieties by means of Acetobacter aceti MIM 2000/28 to afford the corresponding chiral 2-hydroxymethyl alkanoic acids (up to 94 % ee). The procedure, carried out in aqueous medium under mild conditions of pH, temperature and pressure, contributes to enlarge the portfolio of enzymatic oxidations available to organic chemists for the development of sustainable manufacturing processes.
- Brenna, Elisabetta,Cannavale, Flavia,Crotti, Michele,De Vitis, Valerio,Gatti, Francesco G.,Migliazza, Gaia,Molinari, Francesco,Parmeggiani, Fabio,Romano, Diego,Santangelo, Sara
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p. 3796 - 3803
(2016/12/24)
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- Direct oxidative lactonization of alkenoic acids mediated solely by NaIO4: Beyond a simple oxidant
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Triflic acid-catalyzed direct oxidative lactonization of alkenoic acids mediated solely by NaIO4 without halogen salts is described. Sodium periodate works not only as an oxidant, but also as an active reagent and directly mediates the lactonization. A new cheap, green, and practical oxidative lactonization approach has been developed using NaIO4 as the sole reagent.
- Kang, Yan-Biao,Chen, Xian-Min,Yao, Chuan-Zhi,Ning, Xiao-Shan
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supporting information
p. 6193 - 6196
(2016/05/19)
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- N -Boc amines to oxazolidinones via Pd(II)/bis-sulfoxide/br?nsted acid Co-catalyzed allylic C-H oxidation
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A Pd(II)/bis-sulfoxide/Br?nsted acid catalyzed allylic C-H oxidation reaction for the synthesis of oxazolidinones from simple N-Boc amines is reported. A range of oxazolidinones are furnished in good yields (avg 63%) and excellent diastereoselectivities (avg 15:1) to furnish products regioisomeric from those previously obtained using allylic C-H amination reactions. Mechanistic studies suggest the role of the phosphoric acid is to furnish a Pd(II)bis-sulfoxide phosphate catalyst that promotes allylic C-H cleavage and π-allylPd functionalization with a weak, aprotic oxygen nucleophile and to assist in catalyst regeneration.
- Osberger, Thomas J.,White, M. Christina
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supporting information
p. 11176 - 11181
(2014/08/18)
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- Use of ethyl (benzothiazol-2-ylsulfonyl)acetate for malonic ester-type syntheses of carboxylic acids and esters
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A new methodology for the synthesis of substituted carboxylic acids is described. Alkylation of either ethyl (benzothiazol-2-ylsulfonyl)acetate or ethyl 2-(benzothiazol-2-ylsulfonyl)propionate was achieved with alkyl halides and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in dichloromethane solution. These products were then desulfinated and hydrolysed in one-pot under mild conditions to give substituted acetic acids in good-to-excellent yields.
- Hussein, Waleed M.,McGeary, Ross P.
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p. 1222 - 1227
(2014/10/16)
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- Palladium-catalyzed allylic alkylation of doubly deprotonated carboxylic acids
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Doubly deprotonated carboxylic acids undergo smooth palladium-catalyzed carbon alkylations with the allylic substrates methyl allyl carbonate and (E)-methyl (pent-3-en-2-yl) carbonate to give γ,δ-unsaturated carboxylic acids. A diastereoselective and enantioselective protocol leads to (2S,3R)-hexenoic acid in 87% ee. Copyright
- Braun, Manfred,Meletis, Panos,Visse, Robin
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experimental part
p. 3380 - 3384
(2012/02/02)
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- Total synthesis of (+)-(2′S,3′R)-zoapatanol exploiting the B-alkyl Suzuki reaction and the nucleophilic potential of the sulfinyl group
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A stereoselective synthesis of the diterpenoid oxepane (+)-zoapatanol is described. The key steps include a B-alkyl Suzuki cross-coupling reaction for the stereoselective synthesis of trisubstituted alkenes, creation of the two stereogenic centers on the oxepane ring by heterofunctionalization of an alkene through substrate control exploiting the nucleophilic potential of an intramolecular sulfinyl group, and transformation of a β-hydroxy sulfoxide into a terminal alkene. Copyright
- Raghavan, Sadagopan,Sudheerbabu, Vaddela
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supporting information; experimental part
p. 8487 - 8494
(2011/09/12)
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- Highly chemo- and enantioselective synthesis of 3-Allyl-3-aryl oxindoles via the direct palladium-catalyzed α-arylation of amides
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Figure presented A new NHC·Pd-catalyzed asymmetric α-arylation of amides is reported that gives direct access to synthetically valuable, allylated oxindoles with quaternary carbon centers. The reaction is made possible by the introduction of a new chiral NHC ligand. The palladium complexes derived therefrom combine excellent reactivity with high chemo- and enantioselectivity for the title transformation.
- Luan, Xinjun,Wu, Linglin,Drinkel, Emma,Mariz, Ronaldo,Gatti, Michele,Dorta, Reto
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supporting information; experimental part
p. 1912 - 1915
(2010/07/06)
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- Striking AcOH acceleration in direct intramolecular allylie amination reactions
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An experiment was conducted to demonstrate that a strong accelerating effect occurs in direct intramolecular allylic amination when the reaction is conducted in AcOH rather than in CHCl or THF. A round bottom flask under air was charged with N-tosylcarbamate 3a-j, Pd(OAc)2, bis-sulfoxide ligand LL, phenylbenzoquinone and AcOH. The reaction was allowed to stir at 45°C for 24 h. The reaction mixture was hydrolysed and extracted with AcOEt. The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Cyclisation of 3a was repeated in CH2Cl 2 and in AcOH by using stoichiometric amounts of Pd(OAc) without benzoquinone. Stoichiometric tests and computational DFT analysis of the palladium reoxidation step provide an overview of the structural and energetic role of acetic acid in increasing the efficacy of the entire catalytic cycle.
- Nahra, Fady,Liron, Frederic,Prestat, Guillaume,Mealli, Carlo,Messaoudi, Abdelatif,Poli, Giovanni
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supporting information; experimental part
p. 11078 - 11082
(2010/04/28)
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- Synthetic approaches and total synthesis of natural zoapatanol
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(Chemical Equation Presented) The total synthesis of (+)-zoapatanol utilizing an intramolecular Horner-Wadsworth-Emmons olefination and an enantioselective Sharpless dihydroxylation as the key steps has been achieved. An advanced oxepene intermediate has been obtained by applying a ring-closing metathesis to an unsaturated enol ether.
- Taillier, Catherine,Gille, Barbara,Bellosta, Veronique,Cossy, Janine
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p. 2097 - 2108
(2007/10/03)
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- Construction of vicinal quaternary carbon atoms by Ireland ester Claisen rearrangement: Total synthesis of (±)-herbertenolide, (±)-herberteneacetal, (±)-herbertene-1,14-diol and (±)-herbertene-1,15-diol
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Efficient total syntheses of the herbertane sesquiterpene title compounds have been accomplished employing an Ireland ester Claisen rearrangement and ring-closing metathesis reaction sequence based strategy for the construction of two stereogenic vicinal quaternary carbon atoms on a cyclopentane.
- Srikrishna,Vasantha Lakshmi
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p. 4879 - 4881
(2007/10/03)
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- Self-Protection: The Advantage of Radical Oligomeric Mixtures in Organic Synthesis
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Atom-transfer radical oligomers of allyl iodoacetates were converted to 4-pentenoic acids upon treatment with zinc. Reactions of the radical oligomers of various ω-alkenyl iodoacetates with Grignard reagents afforded the corresponding substituted tetrahydrofuran derivatives. These results indicated that radical oligomeric mixtures not only serve as versatile intermediates in organic synthesis, but also exhibit unique advantages in that the oligomeric mixtures are self-protected and the deoligomerization functions as the simultaneous deprotection.
- Yu, Hui,Li, Chaozhong
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p. 142 - 145
(2007/10/03)
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- Total synthesis of natural (+)-(2′S,3′R)-zoapatanol
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(+)-Zoapatanol was synthesized by using four key-steps: a Suzuki cross-coupling to prepare a (Z)-α,β-unsaturated ester followed by an enantioselective dihydroxylation to control the C2′ and C3′ stereocenters, an intramolecular Horner-Wadsworth-Emmons olefination to construct the oxepane ring, and a chemoselective nucleophilic addition/Birch reduction process of a Weinreb amide to introduce simultaneously the β,γ-unsaturated ketone on the side-chain and regenerate alcohols from benzyl ethers.
- Taillier, Catherine,Bellosta, Veronique,Cossy, Janine
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p. 2149 - 2151
(2007/10/03)
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- Copper(I) catalysts for the stereoselective addition of N-chloroamines to double bonds: A diastereoselective radical cyclisation
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Copper(I) catalysts for the diastereoselective radical cyclisation of N-chloro-N-pentenylamines have been developed. The stereoselectivity of the cyclisation depends upon the ligands employed, proving that the radical is bound to the catalyst during the formation of the new stereocentre and making a catalyst-influenced stereoselective radical reaction possible. The influence of the catalyst on the Beckwith-Houk transition states is discussed. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
- Heuger, Gerold,Kalsow, Stefanie,Gottlich, Richard
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p. 1848 - 1854
(2007/10/03)
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- Free radical reactions on soluble supports from ring-opening metathesis
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Equation presented Free radical reactions were performed on soluble ring-opening metathesis (ROM) polymers. These polymers have high substrate loading, short reaction times, and the benefit of a facile purification. All reactions on these supports were obtained in good yields as white crystalline-like materials readily separated from tin byproducts.
- Enholm, Eric J.,Gallagher, Maria E.
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p. 3397 - 3399
(2007/10/03)
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- Intermolecular free radical reactions on solid support. Allylation of esters
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The first examples of intermolecular free radical allylation reactions on solid support are reported. The allylation proceeds in good chemical efficiency with a variety of substrates as well as allylating agents. Control experiments indicate that the polymer matrix is inert to the reaction conditions.
- Sibi, Mukund P.,Chandramouli, Sithamalli V.
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p. 8929 - 8932
(2007/10/03)
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- Oxidative Decarboxylation of Cyclohexane Monocarboxylic Acid as a Degenerate Branching Chain Reaction. I. Kinetics
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Kinetics of product accumulation during the oxidative decarboxylation of cyclohexane monocarboxylic acid has been followed by GCMS, inhibitor and chemiluminescence methods.Results indicate that in the degenerate branching chain process selective (peroxy) radicals abstract predominantly tertiary hydrogen atoms from the substrate while non-selective (e.g. hydroxyl, alkoxy) radicals attack also secondary hydrogen atoms.The rate constant of the chain propagation was found to be kp = 7.5*106 exp (-57.6 kJ mol-1/RT) l mol-1 s-1.Furthermore it has been established, that the oxidative decarboxylation proceeds via two parallel pathways: one resulting in cyclohexanone, while the other avoiding the formation of the latter. Key Words: Chemical Kinetics / Elementary Reactions / Radicals / Oxidation, decarboxylation
- Nemes, I.,Heberger, K.,Keszler, A.,Vasvari, G.,Gal, D.,et al.
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- Studies on Cyclodepsipeptides - Part I : A Stereoselective Synthesis of C12 Polyketide Unit (C1-C8) Present in Jaspamide and Geodiamolide A-F
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An innovative synthetic protocol to obtain the polyketide C12 chain in an enantiomerically pure form has been developed.
- Rao, A. V. Rama,Gurjar, Mukund K.,Nallaganchu, Bhaskara Rao,Bhandari, Ashok
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p. 7081 - 7084
(2007/10/02)
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- Antiparasitic agents
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The invention provides novel compounds having the formula: STR1 wherein R when taken individually is H; R1 when taken individually is H or OH; R and R1 when taken together represent a double bond; R2 is an alpha-branched C3 -C8 alkyl, alkenyl, alkynyl, alkoxyalkyl or alkylthioalkyl group; a C3 -C8 cycloalkyl, C5 -C8 cycloalkenyl or C5 -C8 cycloalkylalkyl group, any of which may be substituted by methylene or one or more C1 -C4 alkyl groups or halo atoms; or a 3 to 6 membered oxygen or sulphur containing heterocyclic ring which may be substituted by one or more C1 -C4 alkyl groups or halo atoms; R3 is hydrogen or methyl; R4 is H or 4'-(alpha-L-oleandrosyl)-alpha-L-oleandrosyloxy with the proviso that when R2 is alkyl it is not isopropyl or sec-butyl; when R4 is H, each of R and R1 is H, and R2 is not methyl or ethyl; and when R4 is H, R is H, R1 is OH, and R2 is not 2-buten-2-yl, 2-penten-2-yl or 4-methyl-2-penten-2-yl. The compounds are broad spectrum antiparasitic agents having utility as anthelmintics, ectoparasiticides, insecticides and acaricides. The invention also provides a process for producing the novel avermectin and milbemycin derivatives by adding a carboxylic acid or derivative thereof to a fermentation of an avermectin or milbemycin producing organism.
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- A Facile Method for Synthesis of Three Carbon-Homologated Carboxylic Acid by Regioselective Ring-opening of β-Propiolactones with Organocopper Reagents
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Organocopper reagents, such as diorganocuprates, organocopper-tributylphosphine, and Grignard reagents in the presence of a copper (I) salt, reacted with β-propiolactones by regioselective β-carbon-oxygen fission to give 3-substituted propionic acids.Among these three kinds of organocopper reagents, diorganocuprate, especially halomagnesium cuprate gave the highest yields of the acids, which was remarkably observed in the ring-opening of sterically hindered β-propiolactones such as β-methyl- and α,β-dimethyl-β-propiolactones and also in the reactions using the organocopper reagents with vinyl and allyl substituents.The ring-opening of β-propiolactone was confirmed to proceed by SN2 pathway with predominant inversion of configuration of the β-carbon by using the reaction of cis-α,β-dimethyl-β-propiolactone with di-tert-butylcuprate to afford syn-2,3,4,4-tetramethylpentanoic acid.
- Kawashima, Masatoshi,Sato, Toshio,Fujisawa, Tamotsu
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p. 403 - 412
(2007/10/02)
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- Synthetic Studies Relevant to Biosynthetic Research on Vitamin B12. Part 5. Synthesis of (RS)-Ring-B Imide
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Future biosynthetic research on vitamin B12 depends on the synthesis of a family of isobacteriochlorin pigments.A key building block required for this work is 2-(2-methoxycarbonylethyl)-3-methoxycarbonylmethyl-3-methylsuccinimide, usually called the ring-B imide.A practical synthesis of the racemic form of this substance is described which can yield multigramme quantities of product.
- Battersby, Alan R.,Westwood, Steven W.
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p. 1679 - 1688
(2007/10/02)
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- Synthesis of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones
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An easy synthesis for the 1,3-thiazol-5(4H)-thiones 5, a class of heterocycles which have hitherto only been available with difficulty, is described.Reaction of 3-amino-2H-azirines 25 with thiocarboxylic acids at 0 deg yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100 deg, undergo thiation and cyclization to give 5 in good yield.
- Jenny, Christjohannes,Heimgartner, Heinz
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p. 374 - 388
(2007/10/02)
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- Synthesis of 4-Penten-4-olides (γ-Methylene-γ-butyrolactones) via 4-Pentenoic Acids
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4-Penten-4-olides (γ-Methylene-γ-butyrolactones) 7 are easily accessible starting from allylic alcohols 1, which on ortho ester Claisen rearrangement and hydrolytic work-up furnish 4-pentenoic acids 5.The latter on iodolactonization and hydrogen iodide elimination by means of 1,8-diazabicycloundec-7-ene (DBU) furnish 7, in good over-all yield and with variable substitution patterns. - Iodolactonization under kinetic control shows moderate 1,2- or 1,3-asymmetric induction (3:1 and ca. 2:1, respectively).The composition of the iodolactone mixtures 6 as well as the individual relative configurations are deduced from 1H and 13C NMR data. - Similary, the spirobipentenolide 13 is obtained starting from diethyl diallylmalonate (9) via 11 resulting from ester iodocyclization.
- Guenther, Hans Juergen,Guntrum, Eberhard,Jaeger, Volker
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- A THREE CARBON HOMOLOGATION BY THE RING-OPENING OF β-PROPIOLACTONES WITH DIORGANOCUPRATES
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Various organocuprates react with β-propiolactones to give β-substituted propionic acids in high yields.
- Fujisawa, Tamotsu,Sato, Toshio,Kawara, Tatsuo,Kawashima, Masatoshi
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p. 2181 - 2184
(2007/10/02)
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- One-Step Annelation. A Convenient Method for the Preparation of Diols, Spirolactones, and Spiroethers from Lactones
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1-(ω-Hydroxyalkyl)cyclopentanols and -cyclohexanols were prepared in one step in high yields from butane-1,4-diyl- and pentane-1,5-diylmagnesium dibromides and lactones in tetrahydrofuran.This method was found to be general and applicable to lactones of any size (β, γ, δ, and ε) and structure whether aliphatic, aromatic, bicyclic, or spirocyclic.Evidently important steric hindrance close to the carbonyl group prevents annelation and attack on the second nucleophilic center of the Grignard reagent.Furthermore, in the case of oxetan-2-one one obtains, in additionto the corresponding diol, products resulting from scission of the C-O bond.The diols by appropriate transformation afford new routes to spirolactones and spiroethers.
- Canonne, Persephone,Foscolos, Georges B.,Belanger, Denis
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p. 1828 - 1835
(2007/10/02)
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- COPPER-CATALYZED REACTION OF GRIGNARD REAGENTS WITH β-PROPIOLACTONES: A CONVENIENT METHOD FOR THE SYNTHESIS OF Β-SUBSTITUTED PROPIONIC ACIDS
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Grignard reagents react with β-propiolactones in the presence of a copper(I) catalyst to give β-substituted propionic acids in high yields.
- Sato, Toshio,Kawara, Tatsuo,Kawashima, Masatoshi,Fujisawa, Tamotsu
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p. 571 - 574
(2007/10/02)
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