- Aromatic ring synthesis by 1,3-Michael-Claisen annulation: Application to a Trolox analogue and to Precocene II
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A Trolox analogue, 3,4-dihydro-2-ethoxycarbonyl-6-methoxy-7-hydroxybenzopyran and Precocene II, were prepared from substituted α-methylene-δ-valerolactone and 1,1-bis-(methylthio)-2-propanone or butanone, via a 1,3-Michael-Claisen annulation.
- Solladie,Boeffel,Maignan
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Read Online
- Cooperative Polar/Steric Strategy in Achieving Site-Selective Photocatalyzed C(sp3)?H Functionalization
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Synergistic control over the SH2 transition states of hydrogen abstraction exploiting polar and steric effects provides a promising cooperative strategy for site-selective C(sp3)?H functionalization using decatungstate anion photocatalysis. By using this photocatalytic approach, the C?H bonds of substituted lactones and cyclic ketones were functionalized selectively. In the remarkable case of 2-isoamyl 4-tert-butyl cyclohexanone (1 t) bearing five methyl, five methylene, and three methine C?H bonds, one methine C?H bond in the isoamyl tether was selectively functionalized.
- Yamada, Keiichi,Fukuyama, Takahide,Fujii, Saki,Ravelli, Davide,Fagnoni, Maurizio,Ryu, Ilhyong
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- Synthesis of the ester side chains of homoharringtonine and harringtonine using lactones as building blocks
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The efficient synthesis of the ester side chains of homoharringtonine and harringtonine using lactones as building blocks has been developed. The synthesis used classic reactions from readily available starting materials. Reactions of the lactone bearing
- Dang, Fang-Fang,Wang, Cui-Cui,Han, Feng,Zhang, Zhi-Wei
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supporting information
p. 317 - 323
(2020/10/14)
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- Green Oxidation of Ketones to Lactones with Oxone in Water
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Cyclic ketones were quickly and quantitatively converted to 5-, 6-, and 7-membered lactones, very important synthons, by treatment with Oxone, a cheap, stable, and nonpollutant oxidizing reagent, in 1 M NaH2PO4/Na2HPO4 water solution (pH 7). Under such simple and green conditions, no hydroxyacid was formed, thus making the adoption of more complex and non-eco-friendly procedures previously developed to avoid lactone hydrolysis unnecessary. With some changes, the method was successfully applied also to water-insoluble ketones such as adamantanone, acetophenone, 2-indanone, and the challenging cycloheptanone.
- Bertolini, Valentina,Appiani, Rebecca,Pallavicini, Marco,Bolchi, Cristiano
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p. 15712 - 15716
(2021/11/01)
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- Calcium(II)- And Triflimide-Catalyzed Intramolecular Hydroacyloxylation of Unactivated Alkenes in Hexafluoroisopropanol
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We report an efficient intramolecular hydroacyloxylation of unactivated alkenes, offering a streamlined access to relevant γ-lactones, which features the utilization of either a calcium(II) salt or triflimide as a catalyst in hexafluoroisopropanol. This method could be applied to the synthesis of natural products and the late-stage functionalization of natural and bioactive molecules. Additionally, DFT computations were used to elucidate the twist of reactivity observed between the hydroamidation and hydroacyloxylation of unactivated alkenes regarding the formation of 5- and 6-membered rings.
- Qi, Chenxiao,Yang, Shengwen,Gandon, Vincent,Leb?uf, David
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supporting information
p. 7405 - 7409
(2019/10/02)
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- C-H oxygenation at tertiary carbon centers using iodine oxidant
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An oxidation system in which iodic acid (HIO3) is used as an oxidant in the presence of N-hydroxyphthalimide (NHPI) permitted the selective hydroxylation of tertiary C-H bonds and the lactonization of carboxylic acids containing a tertiary carbon center. These reactions are operationally simple and proceed under metal-free conditions using commercially available reagents, thus offering an ideal tool for the efficient oxidation of C-H bonds at tertiary carbon centers.
- Kiyokawa, Kensuke,Ito, Ryo,Takemoto, Kenta,Minakata, Satoshi
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supporting information
p. 7609 - 7612
(2018/07/15)
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- Formation of δ-Lactones with anti-Baeyer–Villiger Regiochemistry: Investigations into the Mechanism of the Cerium-Catalyzed Aerobic Coupling of β-Oxoesters with Enol Acetates
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The cerium-catalyzed, aerobic coupling of β-oxoesters with enol acetates and dioxygen yields δ-lactones with a 1,4-diketone moiety. In contrast to the Baeyer–Villiger oxidation (BVO), where the higher substituted residue migrates; in the case of this oxid
- Geibel, Irina,Dierks, Anna,Müller, Thomas,Christoffers, Jens
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p. 7245 - 7254
(2017/05/31)
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- Efficient and Selective Cu/Nitroxyl-Catalyzed Methods for Aerobic Oxidative Lactonization of Diols
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Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
- Xie, Xiaomin,Stahl, Shannon S.
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supporting information
p. 3767 - 3770
(2015/04/14)
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- Highly practical copper(I)/TEMPO catalyst system for chemoselective aerobic oxidation of primary alcohols
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Aerobic oxidation reactions have been the focus of considerable attention, but their use in mainstream organic chemistry has been constrained by limitations in their synthetic scope and by practical factors, such as the use of pure O2 as the oxidant or complex catalyst synthesis. Here, we report a new (bpy)CuI/TEMPO catalyst system that enables efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and the high selectivity for 1° alcohols enables selective oxidation of diols that lack protecting groups.
- Hoover, Jessica M.,Stahl, Shannon S.
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supporting information; experimental part
p. 16901 - 16910
(2011/12/04)
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- Structural and stereochemical requirements of the spiroketal group of hippuristanol for antiproliferative activity
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Hippuristanol is a natural product that has recently been shown to inhibit eukaryotic translation initiation and tumor cell proliferation. To investigate the structure and activity relationship of hippuristanol, we synthesized a series of analogs by expan
- Li, Wei,Dang, Yongjun,Liu, Jun O.,Yu, Biao
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scheme or table
p. 3112 - 3115
(2010/09/08)
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- Cycloisomerization of olefinic carboxylic acids catalyzed by trifluoromethanesulfonic acid
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The trifluoromethanesulfonic acid-catalyzed cyclization of various differently substituted unsaturated carboxylic acids affords selectively substituted lactones in good yields. The reactions use 0.5 to 5% molar ratio of catalyst and can be run without solvent.
- Coulombel, Lydie,Dunach, Elisabet
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p. 153 - 160
(2007/10/03)
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- Pd(II)-hydrotalcite-catalyzed selective oxidation of alcohols using molecular oxygen
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A novel heterogenized Pd catalyst, Pd supported by hydrotalcite [Pd(II)-hydrotalcite], was synthesized by a simple operation from commercially available hydrotalcite, Pd(OAc)2 and pyridine. The catalyst was effective for the oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant. With this catalytic system, various alcohols were readily converted to the corresponding aldehydes or ketones selectively in high to excellent yields. Sterically less hindered substrates were converted to the corresponding ketones much faster than the hindered ones. For example, cyclohexanol was converted to cyclohexanone in 79% yield for 15 hr, while larger-sized cyclic alcohols were oxidized to the corresponding ketones only in 32-77% yields in the same reaction time. The catalyst was also applicable to the oxidation of unsaturated alcohols such as geraniol and nerol without any isomerization of an alkenic part. Modified Pd(II)-hydrotalcite [Pd(II)-hydrotalcite(m)] could be reused several times while keeping its activity.
- Uemura,Kakiuchi,Nishimura,Inoue
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p. 165 - 172
(2007/10/03)
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- A new synthesis of lactones from tertiary alkenylcarbinols by cobalt-catalyzed photocarbonylation under ambient conditions
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In the presence of a Co catalyst, tertiary vinyl-, propenyl-, and allylcarbinols were chelatively cycloadded to carbon monoxide to produce lactones by xanthone-sensitized photoreaction in tetrahydrofuran, under CO at 1 atmosphere and at room temperature.At lower temperatures the isomerization of alkenyl-carbinols was suppressed and lactones were obtained with improved selectivity.The photoprocess was facilitated by addition of pyridine or hydrogen and retarded in presence of amines or phosphines.Mechanistic interpretations for the process and the accompanying effects are discussed.Key words: chelative carbonylation, photocarbonylation, carbonylation of olefins, lactones synthesis from alkenylalcohols.
- Chow, Yuan L.,Huang, Yu-Jin,Dragojlovic, Veljko
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p. 740 - 742
(2007/10/02)
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- Heterogeneous Baeyer-Villiger Oxidation of Ketones using an Oxidant consisting of Molecular Oxygen and Aldehydes in the Presence of Hydrotalcite Catalysts
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Hydrotalcites catalyse Baeyer-Villiger oxidation of ketones using a combination oxidant system of molecular oxygen and benzaldehyde to give high yields of lactones and esters at 40 deg C.
- Kaneda, Kiyotomi,Ueno, Shinji,Imanaka, Toshinobu
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p. 797 - 798
(2007/10/02)
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- DIRECT SYNTHESIS OF δ-LACTONES FROM 2-(3-LITHIOPROPYL)-1,3-DIOXOLANE AND CARBONYL COMPOUNDS
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The reaction of 2-(3-lithiopropyl)-1,3-dioxolane (2), prepared in situ by lithiation of the chloroacetal 1 with lithium naphthalenide at -78 deg C, with aldehydes and ketones followed by hydrolysis with hydrochloric acid and final oxidation with PCC or Jones reagent yields the corresponding δ-lactones 5.
- Ramon, Diego J.,Yus, Miguel
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p. 3767 - 3770
(2007/10/02)
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- Lactones, XX. - Grignardation Followed by Phase-Transfer Oxidation: A Convenient Synthesis of δ,δ-Disubstituted δ-Lactones from δ-Valerolactone
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A Grignardation-oxidation sequence, without isolation of intermediates, easily transfers δ-valerolactone (4) into Δ,δ-disubstituted δ-lactones 6.The synthesis of δ,δ-diphenyl-δ-valerolactone (6a) served as an exsample for a detailed investigation of the r
- Lehmann, Jochen,Marquardt, Norbert
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p. 827 - 832
(2007/10/02)
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- SUBSTITUENT DIRECTED OXIDATIVE CYCLIZATION WITH CETYLTRIMETHYLAMMONIUM PERMANGANATE: A GENERAL APPROACH TO THE SYNTHESIS OF γ- AND δ-LACTONES
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Treatment of primary, secondary or tertiary γ- and δ-hydroxyolefins with cetyltrimethylammonium permanganate gives good yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon.
- Rathore, Rajendra,Vankar, Padma S.,Chandrasekaran, S.
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p. 4079 - 4082
(2007/10/02)
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- Chemoselective Addition of Organotitanium Reagents to Carbonyl Compounds
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The conversion of classical carbanions such as RMgX, RLi, or deprotonated nitriles, sulfones, and carboxylic esters into titanium analogs results in reagents which add chemoselectively to carbonyl compounds in the presence of other functional groups.The standard titanating agent is chlorotriisopropoxytitanium (1).Grignard-type reactions and aldol additions are aldehyde-selective in the presence of ketones.Other functional groups such as alkyl and aryl halides, esters, amides as well as nitro and cyano moieties are tolerated.Discrimination between two aldehydes or two ketones is also possible.Replacing alkoxy ligands by methyl groups at titanium increases reactivity dramatically, relative rates increasing in the series CH3Ti(OCHMe2)3 (CH3)2Ti(OCHMe2)2 (CH3)4Ti.The latter reagent and its zirconium analog methylate sterically hindered and/or enolizable ketones which normally fail to undergo Grignard reactions.The ate complex H2C=CHCH2Ti(OCHMe2)4MgCl (63) is aldehyde-selective, while the amino analog H2C=CHCH2Ti(NMe2)4MgCl (64) adds selectively to ketones in the presence of aldehydes.
- Reetz, Manfred T.,Westermann, Juergen,Steinbach, Rainer,Wenderoth, Bernd,Peter, Roland,et al.
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p. 1421 - 1440
(2007/10/02)
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- A HIGHLY EFFICIENT SYNTHESIS OF γ- AND δ-LACTONES BY OXIDATIVE CYCLIZATION
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Treatment of tertiary γ- and δ-hydroxyolefins with pentavalent chromium reagent, (BipyH2)CrOCl5, give good yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon.Pyridinium chlorochromate (PCC) also effect this transformation to γ-lactones in reasonable yields.
- Chakraborty, T. K.,Chandrasekaran, S.
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p. 551 - 554
(2007/10/02)
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- TOTAL SYNTHESIS OF CATALPALACTONE
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The first synthesis of catalpalactone (1) is reported.The key steps are the coupling of the selenenylated lactone 8 with bromophthalide (9) and the selenoxide elimination of 14 to give catalpalactone with very high regioselectivity.
- Marx, John N.,Dobrowolski, Paul J.
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p. 4457 - 4460
(2007/10/02)
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