- A new experimental protocol for intrazeolite photooxidations. The first product-based estimate of an upper limit for the intrazeolite singlet oxygen lifetime
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The intrazeolite photooxidations of several alkenes have been examined in hexane and in perfluorohexane slurries. The ability of perfluorohexane to increase the affinity of alkenes for the interior of the zeolite was documented. The nearly identical reaction rates in the two slurry solvents are attributed to a leveling of the singlet oxygen lifetime by the zeolite framework. A consideration of the rates of the various intrazeolite processes was used to estimate an upper limit for the intrazeolite lifetime of singlet oxygen. Copyright
- Pace, Andrea,Clennan, Edward L.
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- Regioselective formation of silylated cyclobutenes by the photochemical [2+2] cycloaddition of 2(5H)-furanones to trialkylsilylacetylenes
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Enantiopure 5-alkyl-4-methyl-2(5H)-furanones reacted by [2+2] photochemical cycloaddition with several trialkylsilylacetylenes to afford regioselectively 3-oxabicyclo[3.2.0]hept-6-en-2-ones silylated at the vinylic C-7 atom. The possible reasons for such regioselectivity are discussed. The anti/syn stereoselectivity of the photocycloaddition depends on the nature of the alkyl group on the silicon atom in the starting silylacetylenes. The photochemical cycloaddition of 2(5H)-furanones to trialkylsilylacetylenes regioselectively afforded cyclobutenes fused with furanone systems. Copyright
- D'Annibale, Andrea,D'Auria, Maurizio,Mancini, Giovanna,Pace, Alessio Daniel,Racioppi, Rocco
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- Palladium/Norbornene-Catalyzed ortho Aliphatic Acylation with Mixed Anhydride: Selectivity and Reactivity
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A palladium/norbornene-catalyzed ortho acylation for the efficient synthesis of functionalized alkyl aryl ketones is reported. Studies on the electronic and steric properties of mixed aryl anhydrides indicated that the cross-coupling favored with the elec
- Xu, Shibo,Jiang, Julong,Ding, Linlin,Fu, Yao,Gu, Zhenhua
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- Kinetic Resolution of Allyltriflamides through a Pd-Catalyzed C-H Functionalization with Allenes: Asymmetric Assembly of Tetrahydropyridines
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Enantioenriched, six-membered azacycles are essential structural motifs in many products of pharmaceutical or agrochemical interest. Here we report a simple and practical method for enantioselective assembly of tetrahydropyridines, which is paired to a ki
- González, José Manuel,Cendón, Borja,Mascare?as, José Luis,Gulías, Moisés
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supporting information
p. 3747 - 3752
(2021/04/06)
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- Palladium-catalyzed intramolecular reductive olefin hydrocarbonation: Benzylic hydrogen serving as a new hydrogen donor
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A palladium-catalyzed intramolecular hydrocarbonation of unactivated alkenes was achieved, in which toluene is used as a hydrogen donor for the first time. The radical transfer hydrogenation is designed and realized based on the Bond Dissociation Energy (
- Dong, Xu,Cui, Jie,Song, Jian,Han, Ying,Liu, Qing,Dong, Yunhui,Liu, Hui
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supporting information
p. 4903 - 4906
(2017/07/11)
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- Zeolite matrix assisted decomposition of singlet oxygen sensitizers during photooxidation
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Thiazine dyes such as thionine, methylene blue and methylene green were exchanged within monovalent cation exchanged Y zeolites. Depending on the water content the dye molecules exist as either monomer (‘dry’) or dimer (‘wet’). The monomeric dye is effect
- Shailaja,Sivaguru,Ramamurthy
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p. 197 - 205
(2016/11/16)
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- Copper Hydride Catalyzed Reductive Claisen Rearrangements
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An efficient reductive Claisen rearrangement, catalyzed by in situ generated copper hydride and stoichiometric in diethoxymethylsilane, has been developed. Yields of up to 95 ;% with good to excellent diastereoselectivities were observed in this reaction. Mechanistic studies showed that the stereospecific rearrangement proceeded via a chair transition state of (E)-silyl ketene acetals as intermediates and not via the copper enolates.
- Wong, Kong Ching,Ng, Elvis,Wong, Wing-Tak,Chiu, Pauline
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supporting information
p. 3709 - 3712
(2016/03/08)
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- Highly diastereoselective hydrosilylations of allylic alcohols
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The highly syn-selective hydrosilylation of allylic alcohols was developed which, following oxidation, provided 1,3 alcohols containing two contiguous stereocentres. Through judicious choice of silane the complementary anti-selective hydrosilylation was a
- McLaughlin, Mark G.,Cook, Matthew J.
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supporting information
p. 3501 - 3504
(2014/03/21)
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- Highly regioselective control of 1,2-addition of organolithiums to α,β-unsaturated compounds promoted by lithium bromide in 2-methyltetrahydrofuran: A facile and eco-friendly access to allylic alcohols and amines
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Very high regioselective 1,2-addition of organolithiums to α,α-unsaturated carbonyl-like compounds (ketones, aldehydes, and imines) in the presence of LiBr was achieved by carrying out reactions in the sustainable solvent 2-methyltetrahydrofuran. Excellent yields (in isolated product) of allylic alcohols and allylic amines were recovered under a simple experimental procedure at 0 °C.
- Pace, Vittorio,Castoldi, Laura,Hoyos, Pilar,Sinisterra, José Vicente,Pregnolato, Massimo,Sánchez-Montero, Ma. José
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supporting information; experimental part
p. 2670 - 2675
(2011/04/23)
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- Stereoselective synthesis of trisubstituted olefins by a directed allylic substitution strategy
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New methodology for the stereoselective synthesis of trisubstituted olefins is presented. The use of ortho-diphenylphosphanyl benzoate (o-DPPB) as a directing leaving group for copper-mediated allylic substitution with Grignard reagents allowed for the stereoselective construction of a wide range of E olefins, without the need for an adjacent electron-withdrawing group. Our modular three-step approach toward trisubstituted alkenes commenced with geminal α-methylene aldehydes. Addition of an organometallic reagent and introduction of the o-DPPB group by esterification was followed by the o-DPPB-directed copper-mediated allylic substitution with a Grignard reagent to furnish stereodefined trisubstituted olefins. Additionally, incorporation of a stereocenter from the chiral pool allowed the preparation of an enantiomerically pure olefin that bore three alkyl substituents in high E/Z selectivity.
- Schmidt, Yvonne,Breit, Bernhard
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supporting information; experimental part
p. 11780 - 11788
(2011/11/06)
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- Cross-metathesis reactions of homoallyl methyl malonates with sterically hindered allylic esters
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The methyl malonate esters of 3-buten-1-ol and 2-methyl-3-buten-1-ol can be coupled efficiently to different methallylic esters in the presence of the second-generation Grubbs catalyst to yield trisubstituted olefins by the cross-metathesis reaction. Product selectivity and yields depend on the relative amounts of reagents and to a minor extent on the methallylic ester functional group. Alkyl substituents at either the allylic or the geminal positions significantly affect the product yields and the E/Z stereoselectivity. The cross-metathesis reactions of homoallyl malonates with allylic esters featuring a variety of alkyl substituents at the vinylic and/or allylic positions afford trisubstituted olefins. Copyright
- Barile, Fabio,Bassetti, Mauro,D'Annibale, Andrea,Gerometta, Renzo,Palazzi, Michele
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experimental part
p. 6519 - 6526
(2011/12/05)
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- γ-Alumina-supported [60]fullerene catalysts: Synthesis, properties and applications in the photooxidation of alkenes
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Immobilization of [60]fullerene onto γ-Al2O3 surface provides new heterogeneous photocatalysts for the oxidation of organic compounds under oxygen atmosphere. These catalysts have been prepared by simple or successive incipient wetness impregnation (using an organic solvent) followed by air-heating at 180 °C. In the C60/Al2O3 system, C60 loading was varied in the range of 1-4% (w/w). Several experimental techniques including BET, XRD, DRS, TGA, microelectrophoresis, photoluminescence and kinetic extraction, have been used to characterize these catalytic materials. It was found that the quite high surface exposed by the supported C60 increases with the amount of the supported C60, while the dispersion of the supported C60 decreases. The quite stable supported [60]fullerene phase is comprised from C60 clusters, small and large aggregates. This non-uniform size distribution is reflected to a non-uniform distribution concerning the 'supported phase-support' interactions. These interactions decrease with the amount of the supported C60. The photocatalysts prepared may be safely used up to 200 °C. Above this temperature the supported C60 is sublimated/combusted in air. The photocatalytic activity of the so-obtained catalytic systems has been evaluated in terms of substrate conversion in the singlet oxygen 'ene' reaction of alkenes. The photooxygenation of 2-methyl-2-heptene has been examined as a probe reaction. It was found that the catalytic activity increases with the increasing amount of the supported C60 up to the value of 3% (w/w) and then decreases. The intrinsic activity expressed as TON or TOF decreased monotonically with C60. In all cases, however, the photocatalytic activity of the Al2O3-supported C60 catalysts was substantially increased compared to the unsupported C60 precursor, exhibiting quantitative conversion yields after short reaction times. The catalytic behavior was attributed to the aforementioned opposite trends which follow the surface exposed by the supported C60 on one hand and the 'supported C60-support' interactions and the C60 dispersion on the other hand. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis.
- Tzirakis, Manolis D.,Vakros, John,Loukatzikou, Loukia,Amargianitakis, Vasilis,Orfanopoulos, Michael,Kordulis, Christos,Lycourghiotis, Alexis
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experimental part
p. 65 - 74
(2010/05/01)
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- Glycol-modified molybdate catalysts for efficient singlet oxygen generation from hydrogen peroxide
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Pretreatment of molybdate-exchanged layered double hydroxides in polyalcohols such as ethylene glycol affords heterogeneous catalysts showing largely improved oxidant efficiency compared to the unmodified materials. The Royal Society of Chemistry.
- Wahlen, Joos,De Vos, Dirk,Jary, Walther,Alsters, Paul,Jacobs, Pierre
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p. 2333 - 2335
(2008/02/11)
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- Synthesis of α,β-unsaturated 4,5-disubstituted γ-lactones via ring-closing metathesis catalyzed by the first-generation Grubbs' catalyst
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(Chemical Equation Presented) 4-Methyl-5-alkyl-2(5H)-furanones have been prepared by ruthenium-catalyzed ring-closing metathesis of the suitable methallyl acrylates, Despite the electron deficiency of the conjugated double bond and of the gem-disubstitution of the allylic alkene moiety in the starting acrylates, the first-generation Grubbs' catalyst I proved to be an effective promoter for the ring closure, affording the expected butenolides in good to high yields.
- Bassetti, Mauro,D'Annibale, Andrea,Fanfoni, Alessia,Minissi, Franco
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p. 1805 - 1808
(2007/10/03)
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- A facile route to acyclic substituted α,β-unsaturated aldehydes: The allene claisen rearrangement
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(equation presented) Sigmatropic rearrangement of allenyl ethers furnishes α,β-unsaturated aldehydes in good yield.
- Parsons, Philip J.,Thomson, Peter,Taylor, Andrew,Sparks, Timothy
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p. 571 - 572
(2007/10/03)
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- The regioselective 1,4-addition reaction of alkenylboronic acids to α,β,α′,β′-unsaturated ketones
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The effect of substituents on the double bond of α,β-unsaturated ketones for the 1,4-addition reaction rate of alkenylboronic acids induced by cyanuric fluoride was studied in detail. When the steric hindrance around the β-carbon of the unsaturated ketones increased, the 1,4-addition reaction rate significantly decreased. An alkyl substituent on the α-carbon was also found to significantly affect the 1,4-addition reaction. From these results, unsymmetric α,β,α′,β′unsaturated ketones (10a-f) were designed for the regioselective 1,4-addition reaction with alkenylboronic acids (4a-j). Since they have substituents to disturb the 1,4-addition reaction on only one double bond, the alkenylboronic acids reacted with them from only one side to selectively provide γ,δ,α′,β′-unsaturated ketones (11a-q). Further transformations of the resulting γ,δ,α′,β′-unsaturated ketones were also performed.
- Hara, Shoji,Shudoh, Hisashi,Ishimura, Shigeyuki,Suzuki, Akira
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p. 2403 - 2408
(2007/10/03)
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- Enantioselective acetalization of racemic 1,3-alkanediols with l-methone under kinetically controlled conditions
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Racemic 1,3-alkanediols (rac-1) undergo an enantioselective acetalization by treatment with l-methone enol trimethylsilyl ether (10) in the presence of trifluoromethanesulfonic acid (10 mol%) to give thermodynamically less stable spiroacetal 3 (derived fr
- Harada, Toshiro,Tanaka, Sachi,Oku, Akira
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p. 8621 - 8630
(2007/10/02)
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- Palladium-catalysed oxidation of alcohols with carbon tetrachloride, formation of 4,4,4-trichloro ketones from allylic alcohols and carbon tetrachlorid
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Pd salts catalyse oxidation of alcohols with CCl4 in the presence of K2CO3. Primary alcohols are oxidised to esters, and secondary alcohols to ketones. CCl4 is converted to CHCl3. The reaction of allylic alcohols bearing a terminal olefinic bond with CCl4 or BrCCl3 in the presence of palladium catalyst at 110° affords 4,4,4-trichloro ketones. At 40°, simple adducts of CCl4 or BrCCl3 having a halohydrin structure are obtained, which are converted to the corresponding trichloro ketones by the catalysis of palladium. Various halohydrins are converted to ketones by Pd catalysis.
- nagashima, Hideo,Sato, Koji,Tsuii, Jiro
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p. 5645 - 5651
(2007/10/02)
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- ACTION DES DIALKYLCUPRATES DE LITHIUM SUR LES ALDEHYDES α,β-ETHYLENIQUES
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Nearly exclusive 1-4 addition products are obtained by action of lithium dialkylcuprates with α,β-ethylenic aldehydes.Non polar solvents and low temperatures favor this reaction.Only α,β-ethylenic aldehydes having a trisubstituted double bond give a relatively important proportion of 1-2 addition product.
- Chuit, C.,Foulon, J. P.,Normant, J. F.
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p. 2305 - 2310
(2007/10/02)
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- Synthesis of isoprenoid 1,5-dienes
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Aliphatic acids containing an isoprenoid 1,5-diene moiety are prepared in high yields by the selective gamma alkylation of α,β-unsaturated acids with allylic electrophiles. The gamma-regioselectivity of the alkylation is controlled by the use of the dicopper(I) dienolates prepared from the α,β-unsaturated acids. The method offers a particularly facile means for synthesizing isoprenoid 1,5-diene natural products such as farnesoic acid by alkylation of senecioic acid with geranyl bromide; geranoic acid by alkylation of senecioic acid with 3,3-dimethallyl bromide; and dl-lanceol by alkylation of tiglic acid with an allylic bromide derived from dl-limonene. Such products find use in the synthesis of insect pheremones, insect juvenile hormones, and components of perfumes.
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