- Stereoselective Synthesis of cis-2-Ene-1,4-diones via Aerobic Oxidation of Substituted Furans Catalyzed by ABNO/HNO3
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We report a highly efficient and selective catalytic system, ABNO (9-azabicyclo-[3.3.1]nonane N-oxyl)/HNO3, for the aerobic oxidation of substituted furans to cis-2-ene-1,4-diones under mild reaction conditions using oxygen as the oxidant. The catalyst system is amenable to various substituted (mon-, di-, and tri-) furans and tolerates diverse functional groups, including cyano, nitro, naphthyl, ketone, ester, heterocycle, and even formyl groups. Based on the control and 18O-labeling experiments, the possible mechanism of the oxidation is proposed.
- Yang, Liqun,Wang, Jingyang,Wang, Yue,Li, Xiaotong,Liu, Wei,Zhang, Zhaoguo,Xie, Xiaomin
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supporting information
p. 14311 - 14320
(2021/10/25)
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- Merging singlet-oxygen induced furan oxidations with organocatalysis: Synthesis of enantiopure cyclopentanones and hydrindanes
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A new methodology is described herein which converts simple and readily accesible furan substrates into complex enantio-enriched carbocyclic skeletons through the implementation of a simple one-pot procedure. Singlet oxygen furan photoxygenation affords an enedione which then participates in an organocatalysed double-Michael reaction with an enal to furnish a cyclopentanone structure with up to four new contiguous stereogenic centres. The enantioselectivity and diastereoselectivity of this process are both excellent. If desired, further aldol-annulation steps can be appended to the cascade reaction sequence to afford key enantiopure hydrindane motifs.
- Kalaitzakis, Dimitris,Montagnon, Tamsyn,Sofiadis, Manolis,Tsopanakis, Vasileios,Vassilikogiannakis, Georgios
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supporting information
p. 2817 - 2822
(2020/04/28)
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- Laccase-catalyzed stereoselective oxidative ring opening of 2,5-dialkylfurans into 2-ene-1,4-diones using air as an oxidant
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The laccase-catalyzed ring opening of 2,5-dimethylfuran using air as an oxidant stereoselectively yields (Z)- or (E)-3-hexene-2,5-dione depending on the mediator employed: with TEMPO the (Z)-3-hexene-2,5-dione is formed, while a combination of TEMPO and violuric acid gives (E)-3-hexene-2,5-dione. The (Z)-selective ring cleavage was extended to a variety of symmetrical and unsymmetrical 2,5-dialkylfurans. The Royal Society of Chemistry.
- Asta, Chimene,Conrad, Juergen,Mika, Sabine,Beifuss, Uwe
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scheme or table
p. 3066 - 3069
(2011/12/21)
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- Titanium silicalite 1 (TS-1) catalyzed oxidative transformations of furan derivatives with hydrogen peroxide
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The oxidation of furan derivatives with titanium silicalite 1 (TS-1) and hydrogen peroxide is described. Oxidation products are identified and possible reaction pathways are discussed. It is shown that the oxidation of these compounds occurs via epoxidation of one of the furan double bonds. The initially formed epoxides immediately undergo rearrangement, furans yielding unsaturated 1,4-dicarbonyl compounds and furfuryl alcohols yielding 6-hydroxy-2H-pyran-3(6H) -ones. The latter compounds originate from cyclization of intermediate enedione alcohols. The presented method is particularly useful for the oxidation of 2,5-dimethylfuran to 3-hexene-2,5-dione and the conversion of furfuryl alcohol to 6-hydroxy-2H-pyran-3(6H)-one, a versatile synthon in organic synthesis.
- Wahlen, Joos,Moens, Bart,De Vos, Dirk E.,Alsters, Paul L.,Jacobs, Pierre A.
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p. 333 - 338
(2007/10/03)
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- Thermal and microwave assisted reactions of 2,5-disubstituted thienosultines with [60]fullerene: Non-Kekulé biradicals and self-sensitized oxygenation of the cycloadduct
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Refluxing an o-dichlorobenzene solution of 2,5-disubstituted thienosultines 10a-f with [60]fullerene for 2-24 h gave both 1:1 and 2:1 cycloadducts in 37-79% isolated yields. The reaction was highly accelerated by microwave irradiation giving comparable yields of cycloadducts. Sultines 10a-f underwent cheletropic extrusion of SO2 to form the corresponding non-Kekulé biradical intermediates 11a-f, which were subsequently trapped by [60]fullerene to form corresponding cycloadducts. The activation energy barriers (ΔGc≠) determined for the boat-to-boat inversion of these 4′,5′,6′,7′-tetrahydrobenzo[c]thieno- [5′,6′:1,2][60]fullerene adducts 12a-f were found to be in the range of 13.5-14.8 kcal/mol. Unexpectedly, one of the monoadduct 12a was found to be labile when kept in air under ambient light. Two new products 15 (a sulfine-enone) and 16 (an endione) were isolated from the decomposed 12a and were found to derive from self-sensitized singlet oxygen reaction on the 2,5-dimethylthieno moiety of 12a.
- Chi, Chih-Chin,Pai, I-Feng,Chung, Wen-Sheng
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p. 10869 - 10876
(2007/10/03)
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- Products of the gas-phase reactions of OH radicals with p-xylene and 1,2,3- and 1,2,4-trimethylbenzene: Effect of NO2 concentration
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Aromatic hydrocarbons are important constituents of gasoline fuels, vehicle exhaust, and ambient air in urban areas. In the troposphere, aromatic hydrocarbons, e.g., BTEX and trimethylbenzenes, react essentially only with the hydroxyl (OH) radical. Several product studies of the reaction of OH radicals with BTX and trimethylbenzenes have been conducted, but few of these determined product yields under conditions where the reaction of the OH-aromatic adducts with O2 clearly dominates. GC was used to measure products of the gas-phase reactions of the OH radical with p-xylene and 1,2,3- and 1,2,4-trimethylbenzene in the presence of varying NO2 concentrations. Product analyses showed that the ring-cleavage products 2,3-butanedione and 3-hexene-2,5-dione displayed a dependence of their formation yields on the NO2 concentration, with higher yields from the reactions of the OH-aromatic adducts with O2 than from their reactions with NO2. These ring-cleavage products were primary products of the OH-aromatic adduct reactions. Formation yields extrapolated to zero NO2 concentration should be applicable to ambient atmospheric conditions. The formation yields of 3-hexene-2,5-dione from p-xylene and 1,2,4-trimethylbenzene were comparable to those reported for glyoxal from p-xylene and of methylglyoxal from 1,2,4-trimethylbenzene, thus suggesting that these were coproducts.
- Bethel, Heidi L.,Atkinson, Roger,Arey, Janet
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p. 8922 - 8929
(2007/10/03)
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- Reaction of N-fluoropyridinium salts with Wittig reagents: A novel and convenient approach to symmetric trans-olefins
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N-Fluoropyridinium salts were found to react with Wittig reagents containing electron-withdrawing groups to give olefins in 47-83% yield. The mechanism of this conversion is believed in involve single-electron transfer from Wittig reagent to N-fluoropyridinium cation.
- Kiselyov, Alexander S.
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p. 8951 - 8954
(2007/10/02)
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- Generation and Reactions of Novel Copper Carbenoids through a Stoichiometric Reaction of Copper Metal with gem-Dichlorides in Dimethyl Sulfoxide
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Copper metal and such gem-dichlorides as α,α-dichloro acid esters, 1a-e, diphenyldichloromethane, 2, benzal chloride, 3, 1,1-dichloro-2-butene, 5, and carbon tetrachloride, 6, were found to produce copper carbenoid intermediates via α,α-elimination of dichlorides along with the formation of CuCl2(DMSO)2.Thus, 1 and 2 gave substituted olefins via a carbenoid coupling reaction.From 5 and 6, reaction products via the oxygen abstraction from DMSO were produced together with dimethyl sulfide; 3 and 4 were found to cause both types of reactions.The carbenoid intermediates formed from 1 did not cause cyclopropanation reaction with cyclohexene in contrast to the conventional carbalkoxy carbenoid generated by a decomposition reaction of ethyl diazoacetate.Also the carbenoid coupling reaction was completely inhibited by the addition of triphenylphosphine, which was contrastive to the formation of phosphonium ylide with a carbenoid from ethyl diazoacetate.
- Tezuka, Yasuyuki,Hashimoto, Akio,Ushizaka, Koh,Imai, Kiyokazu
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p. 329 - 333
(2007/10/02)
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- Reactions of Wittig Reagents with Episulfides or Elemental Sulfur
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The reactions of Wittig reagents with episulfides gave symmetrical olefins and triphenylphosphine sulfide in moderate yields.The same olefins were obtained by reactions of Wittig reagents with elementar sulfur.These reactions might proceed through thiocarbonyl intermediates, the existence of which was confirmed by Diels-Alder reactions with dienes.
- Okuma, Kentaro,Tachibana, Yuji,Sakata, Jun-ichi,Komiya, Takashi,Kaneko, Isao,et al.
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p. 4323 - 4328
(2007/10/02)
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- TWO CRYSTALLINE DIMERIC PEROXIDES FROM SENSITIZED PHOTOOXIDATION OF 2,5-DIMETHYLFURAN
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Sensitized photooxidation of 2,5-dimethylfuran was carried out in acetone and dichloromethane.Two crystalline dimeric peroxides were isolated after purified on silica gel.The elucidation of the structures of two dimeric peroxides was based on their spectral and chemical data and X-ray analysis.
- Kuo, Yueh-Hsiung,Shih, Kae-Shyang,Lee, Gene-Hsiang,Wang, Yu
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p. 599 - 604
(2007/10/02)
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- STEREOSELECTIVE SYNTHESIS OF TRANS OLEFINS BY THE REACTION OF WITTIG REAGENTS WITH SELENIUM. FORMATION OF SELENOCARBONYL COMPOUNDS.
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Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium.The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction.
- Okuma, Kentaro,Sakata, Jun-ichi,Tachibana, Yuji,Honda, Takumi,Ohta, Hiroshi
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p. 6649 - 6652
(2007/10/02)
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- Enedione-Functionalized Macrocycles via Oxidative Ring Opening of Furans
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A series of novel polyketo macrocycles was synthesized by oxidative ring opening of the cyclic furan-acetone tetramer 1 and hexamer 2.Reaction of 1 with bromine in acetic acid-water gave the bis(trans-enedione) 3.The use of m-chloroperoxybenzoic acid allowed for the controlled oxidation of 1, giving ring-opened products with the cis-enedione configuration.Reaction using 4.2 equiv of the peracid with 1 gave the tetra-ring-opened octaketone 5 in good yield.Analogously, the hexamer 2, in the reaction with 6.3 equiv of peracid, gave the all-cis unsaturated dodecaketone6.By varying the stoichiometry of the peracid in its reaction with 1, the tri-ring-opened and the two regioisomeric di-ring-opened cis-enediones 7-9, respectively, were isolated.Acid-catalyzed isomerization of 8 and 9 gave the corresponding trans-enediones 3 and 10, respectively, and the structures of these cis and trans isomers were correlated by reduction of the enedione double bonds either by using zinc in acetic acid or by catalytic hydrogenation.The X-ray structures and UV-vis spectra of 3 and 5 are discussed.
- Williams, Peter D.,LeGoff, Eugene
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p. 4143 - 4147
(2007/10/02)
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- The Reaction of Nitrosocarbonyl Compounds with 2,5-Disubstituted Furans. Synthesis of 1,4,2-Dioxazine and 1,4,2-Dioxazole Derivatives
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Oxidation of hydroxamic acids at room temperature in the presence of 2,5-dimethylfuran gives cis-1,4,2-dioxazolylbutenones (5), the structures of which have been confirmed by the synthesis of the dihydro-derivative (12) from the reaction of benzonitrile oxide with hexane-2,5-dione.If the oxidation is carried out at 0 deg C good yields of the unstable furodioxazines (7), the formal products of the addition of furan to the nitrosocarbonyl-arene or -alkane, can be isolated.Compounds (7) are the precursors to (5) and this isomerisation in the oxidation medium is essentially quantitative.It is probably catalysed by an unidentified component, since when pre-isolated (7) is heated the reaction is solvent-dependent and sometimes complex, the amounts of (5) formed being very variable.Nitrosocarbonylbenzene adds to the unsymmetrical compound 2-methyl-5-phenylfuran only at the 2,3-bond, giving the dioxazine (17) and thence the dioxazole (15) exclusively.Secondary amines add readily to the β-carbon of the enone group in (5) while tertiary amines, or more efficiently iodine, convert (5) into the trans-isomers (11). The retro-reaction of (5c) at 80 deg C to dimethylfuran and p-nitronitrosocarbonylbenzene has been demonstrated by trapping the latter, with 1,4-dimethyl-2,3-diphenylcyclopentadiene, as the adduct (21).
- Mackay, Donald,Dao, Le H.,Dust, Julian M.
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p. 2408 - 2416
(2007/10/02)
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