- Copper(i) pyrimidine-2-thiolate cluster-based polymers as bifunctional visible-light-photocatalysts for chemoselective transfer hydrogenation of α,β-unsaturated carbonyls
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The photoinduced chemoselective transfer hydrogenation of unsaturated carbonyls to allylic alcohols has been accomplished using cluster-based MOFs as bifunctional visible photocatalysts. Assemblies of hexanuclear clusters [Cu6(dmpymt)6] (1, Hdmpymt = 4,6-dimethylpyrimidine-2-thione) as metalloligands with CuI or (Ph3P)CuI yielded cluster-based metal organic frameworks (MOFs) {[Cu6(dmpymt)6]2[Cu2(μ-I)2]4(CuI)2}n (2), {[Cu6(dmpymt)6]2[Cu2(μ-I)2]4}n (3), respectively. Nanoparticles (NPs) of 2 and 3 served both as photosensitizers and photocatalysts for the highly chemoselective reduction of unsaturated carbonyl compounds to unsaturated alcohols with high catalytic activity under blue LED irradiation. The photocatalytic system could be reused for several cycles without any obvious loss of efficiency.
- Zhang, Meng Juan,Young, David James,Ma, Ji Long,Shao, Guo Quan
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p. 14899 - 14904
(2021/05/19)
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- Nitrogen-fixing of ultrasmall Pd-based bimetallic nanoclusters on carbon supports
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Synthesis of supported Pd-based bimetallic catalysts is of great importance in the heterogeneous catalysis field owing to their optimal geometric and electronic effects. Downsizing active metals to ultrasmall nanocluster (2-reduction at 400–500 °C. Through the nitrogen-fixing strategy, we prepare 9 sub-2 nm Pd-based bimetallic nanocluster catalysts by conventional impregnation process. The prepared supported bimetallic Pd-Pb nanocluster catalyst exhibit a high turnover frequency of 1092 h?1 for the semihydrogenation of phenylacetylene under a mild condition (30 °C, 5 bar H2), along with a high selectivity of >93% to styrene, demonstrating the alloying and small-size effects in the bimetallic nanocluster catalysts.
- Chen, Ping,Liang, Hai-Wei,Shen, Shan-Cheng,Wang, Lei,Xu, Shi-Long,Yin, Peng,Zhang, Le-Le
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p. 297 - 304
(2020/07/03)
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- Hydrogenative Cyclopropanation and Hydrogenative Metathesis
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The unusual geminal hydrogenation of a propargyl alcohol derivative with [CpXRuCl] as the catalyst entails formation of pianostool ruthenium carbenes in the first place; these reactive intermediates can be intercepted with tethered alkenes to give either cyclopropanes or cyclic olefins as the result of a formal metathesis event. The course of the reaction is critically dependent on the substitution pattern of the alkene trap.
- Peil, Sebastian,Guthertz, Alexandre,Biberger, Tobias,Fürstner, Alois
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supporting information
p. 8851 - 8856
(2019/05/28)
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- Access to Saturated Thiocyano-Containing Azaheterocycles via Selenide-Catalyzed Regio-A nd Stereoselective Thiocyanoaminocyclization of Alkenes
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An efficient route for the synthesis of saturated thiocyano-containing azaheterocycles by selenide-catalyzed regio-A nd stereoselective thiocyanoaminocyclization of alkenes is disclosed. The desired products were obtained in moderate to high yields under mild conditions. The generality of this method was elucidated by its efficient application in thiocyano oxycyclization of alkenes.
- Wei, Wei,Liao, Lihao,Qin, Tian,Zhao, Xiaodan
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supporting information
p. 7846 - 7850
(2019/10/10)
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- Rh-Catalyzed Regioselective Dialkylation of Cage B-H bonds in o-Carboranes: Oxidative Heck Reactions via an Enol Isomerization
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In the presence of a carboxylic acid directing group, Rh-catalyzed regioselective directed dialkylation of B(4,5)-H bonds in o-carboranes and oxidative coupling with allylic alcohols is reported. This strategy constructs a series of 4,5-dialkylated o-carboranes in good yields with excellent regioselectivity. A possible catalytic cycle is proposed that involves a tandem sequence of Rh-catalyzed cage B-H activation, alkene insertion, selective β-H elimination, enol isomerization, and decarboxylation.
- Wang, Qian,Tian, Song,Zhang, Chuyi,Li, Jiangwei,Wang, Zhixuan,Du, Yongmei,Zhou, Ling,Lu, Jian
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supporting information
p. 8018 - 8021
(2019/10/19)
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- Switchable Chemoselective Transfer Hydrogenations of Unsaturated Carbonyls Using Copper(I) N-Donor Thiolate Clusters
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Unsaturated alcohols and saturated carbonyls are important chemical, pharmaceutical, and biochemical intermediates. We herein report an efficient transfer hydrogenation protocol in which conversion of unsaturated carbonyl compounds to either unsaturated alcohols or saturated carbonyls was catalyzed by Cu(I) N-donor thiolate clusters along with changing hydrogen source (isopropanol or butanol) and base (NaOH or K2CO3). Mechanistic studies supported by DFT transition state modeling indicate that such a chemoselectivity can be explained by the relative concentrations of Cu(I) monohydride and protonated Cu(I) hydride complexes in each catalytic system.
- Zhang, Meng-Juan,Tan, Da-Wei,Li, Hong-Xi,Young, David James,Wang, Hui-Fang,Li, Hai-Yan,Lang, Jian-Ping
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p. 1204 - 1215
(2018/02/09)
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- Ruthenium(II)-Catalyzed Regio- and Stereoselective C-H Allylation of Indoles with Allyl Alcohols
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A ruthenium-catalyzed C-H allylation of indoles with allyl alcohols via β-hydroxide elimination is reported. Without external oxidants and expensive additives, this reaction features mild reaction conditions, compatibility with various functional groups, and good to excellent regioselectivity and stereoselectivity.
- Wu, Xiaowei,Ji, Haitao
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supporting information
p. 2224 - 2227
(2018/04/30)
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- Stereoselective Rh-Catalyzed Hydrogenative Desymmetrization of Achiral Substituted 1,4-Dienes
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Highly efficient catalytic stereoselective hydrogenative desymmetrization reactions mediated by rhodium complexes derived from enantiopure phosphine-phosphite (P-OP) ligands are described. The highest performing ligand, which contains a TADDOL-derived phosphite fragment [TADDOL = (2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(diphenylmethanol)], presented excellent catalytic properties for the desymmetrization of a set of achiral 1,4-dienes, providing access to the selective formation of a variety of enantioenriched secondary and tertiary alcohols (six examples, up to 92% ee).
- Fernández-Pérez, Héctor,Lao, Joan R.,Vidal-Ferran, Anton
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supporting information
p. 2836 - 2839
(2016/07/06)
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- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
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The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
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The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
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- Synthesis of Quinolines from Allylic Alcohols via Iridium-Catalyzed Tandem Isomerization/Cyclization Combined with Potassium Hydroxide
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A new tandem catalytic process has been established for the synthesis of quinolines. This process utilizes the [IrCp?Cl2]2/KOH catalyzed isomerization/cyclization of allylic alcohols with 2-aminobenzyl alcohol. Both the secondary and primary allylic alcohols were investigated in this catalytic system to afford different substituted quinoline derivatives in moderate to good yields. A mechanism study showed the reaction following a tandem process integrating isomerization of allylic alcohols and oxidative cyclization of 2-aminobenzyl alcohol.
- Chen, Shu-Jie,Lu, Guo-Ping,Cai, Chun
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p. 976 - 984
(2015/03/30)
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- Alkene migration to the end-terminal carbon bearing a phenyl group over a chiral siloxy carbon center in Heck reaction
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Abstract The Heck reaction of aryl bromide with a terminal alkene substrate having a chiral center at the allylic position and a phenyl substituent at another terminal carbon is reported. An alkene migration to the phenyl-substituted end carbon is observed, along with the typical Heck reaction. This zipper-type migration occurs through multiple internal carbon bonds, and the stereochemistry of the internal chiral center is completely retained during this process.
- Ida, Akiko,Hoshiya, Naoyuki,Uenishi, Jun'ichi
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supporting information
p. 6442 - 6448
(2015/08/18)
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- 1,4-Diazabicyclo[2.2.2]octane-Promoted Aminotrifluoromethylthiolation of α,β-Unsaturated Carbonyl Compounds: N-Trifluoromethylthio-4-nitrophthalimide Acts as Both the Nitrogen and SCF3 Sources
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A novel difunctionalization reaction is described. It uses N-trifluoromethylthio-4-nitrophthalimide as the reagent, which serves as both the nitrogen and SCF3 sources. In the presence of DABCO (1,4-diazabicyclo[2.2.2]octane), the nitrogen and SCF3 groups can be incorporated into α,β-unsaturated carbonyl compounds easily and give versatile β-amino ketones and esters in good yields. This difunctionalization reaction features mild reaction conditions, high atom-economy, and efficient access to α-SCF3 amino acids.
- Xiao, Qing,He, Qijie,Li, Juncheng,Wang, Jun
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supporting information
p. 6090 - 6093
(2016/01/09)
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- Enantioselective synthesis of 3-substituted 1,2-oxazinanes via organocatalytic intramolecular aza-Michael addition
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A highly enantioselective intramolecular 6-exo-trig aza-Michael addition was developed to afford chiral 3-substituted 1,2-oxazinanes in high yields (up to 99% yield) and good enantioselectivities (up to 98/2 er). These reactions were enabled by a quinine-derived primary-tertiary diamine as a catalyst and pentafluoropropionic acid (PFP) as a co-catalyst.
- Cheng, Shuanghua,Yu, Shouyun
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supporting information
p. 8607 - 8610
(2014/12/10)
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- Mesoporous carbon nitride synthesized by nanocasting with urea/formaldehyde and metal-free catalytic oxidation of cyclic olefins
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Mesostructured carbon nitride has been synthesized by nanocasting method with urea/formaldehyde as carbon and nitrogen sources by using disk-shaped 2D hexagonal mesoporous silica (INC-2) as a hard template. The resulted mesoporous carbon nitride (UF-MCN) was characterized as a graphitic structure with hexagonal pores of 3-4 nm and short channels in the submicron range. The catalytic oxidation ability of UF-MCN was demonstrated in the metal-free oxidation of cyclic olefins with hydrogen peroxide. The conversions for cyclopentene, cyclohexene and cis-cyclooctene were obtained in the range of 65-80% and selectivities onto epoxides were 40-90%, respectively. The UF-MCN could illustrate the considerable catalytic oxidation activities due to the existence of surface oxygen species.
- Min, Byung-Hoon,Ansari, Mohd Bismillah,Mo, Yong-Hwan,Park, Sang-Eon
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p. 156 - 163
(2013/08/24)
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- Synthesis of water-tolerant indium homoenolate in aqueous media and its application in the synthesis of 1,4-dicarbonyl compounds via palladium-catalyzed coupling with acid chloride
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The first water-tolerant, ketone-type indium homoenolate was synthesized via the oxidative addition of In/InCl3 to enones. The reaction proceeds exclusively in aqueous media. Both indium and indium(III) chloride are necessary for the smooth conversion of the reaction. Similar results were obtained when InCl or InCl2 was used in place of In/InCl3. The synthetic utility of the indium homoenolate was demonstrated through the synthesis of 1,4-dicarbonyl compounds via palladium-catalyzed coupling of indium homoenolate with acid chloride.
- Shen, Zhi-Liang,Goh, Kelvin Kau Kiat,Cheong, Hao-Lun,Wong, Colin Hong An,Lai, Yin-Chang,Yang, Yong-Sheng,Loh, Teck-Peng
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supporting information; experimental part
p. 15852 - 15855
(2011/01/10)
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- Stereoselectivity in the rhodium-catalysed reductions of nonconjugated dienes
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The stereochemical course of rhodium-catalysed addition of hydrogen and catecholborane to bicyclo[2.2.1]heptadiene, and of hydrogen to a range of cyclic dienes has been analysed. For hydroboration, the overall catalytic reaction possesses exo-selectivity, but the initial step is endo-selective. For hydrogenation (deuteration), the first step may occur with either exo- or endo- selectivity, depending on the structure of the diene. This enables a distinction to be made between pathways involving prior dissociation of the diene, and direct addition to the complexed diene without full dissociation. The relative ease of hydrogenation of the first and second doublebonds varies markedly with reactant structure, and also depends on the choice of catalyst ligands. For dicyclopentadiene, hydrogenation of the cyclopentene double bond is accompanied by rapid alkene isomerisation, as revealed by deuterium addition. The asymmetric hydrogenation of acyclic skipped mesodienes is reported, demonstrating control of relative rates of the two sequential steps, with ees of up to 53% after the first reduction.
- Nguyen, Bao,Brown, John M.
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supporting information; experimental part
p. 1333 - 1343
(2009/12/27)
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- Stereoselective synthesis of 11(E)-tetradecen-1-yl acetate-Sex pheromone of sod webworm (Loxostege sticticalis)
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On the basic of Claisen rearrangement using orthoesters we carried out stereoselective synthesis of 11(E)-tetradecen-1-yl acetate, a sex pheromone of sod webworm (Loxostege sticticalis), which is a specially dangerous pests of crops.
- Shakhmaev,Ishbaeva,Shayakhmetova
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experimental part
p. 1171 - 1174
(2011/05/04)
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- Chiral a-substituted allylboronates in a one-pot three-component asymmetric allylic alkylation/carbonyl allylation reaction sequence -Applications to the syntheses of (+)-(3R,5R)-3-hydroxy-5-decanolide and (-)-massoialactone
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The use of different organomagnesium reagents in the copper-catalyzed allylic alkylation of 3-chloropropenyl with chiral phosphoramidite ligands produces the desired a-substituted allylic boronate reagents in high and with modest to high enantioselectivities (up to 96% ee). The size of the incoming alkyl substituent the organomagnesium reagent was found to impact the yield and selectivity of the allylic alkylation. A one-pot for the preparation of these chiral allylic boronates followed by a Lewis acid (BF3) catalyzed addition to aldehydes the desired allylboration products, homoallylic secondary alcohols, in good yields and very high diastereoselectivity.three-component reaction methodology was applied to the syntheses of two lactone-containing natural , (-)-massoialactone and (+)-(3R,5R)-3-hydroxy-5-decanolide. The key step of these syntheses involved the pot enantioselective copper-catalyzed allylic alkylation/allylboration reaction with a benzylic aldehyde, and the desired product in 87% yield, 92% e,and high E/Z selectivity in a ratio of 22:1. Remarkably, the alkylation step of this sequential reaction was performed with a low catalyst loading of 2 mol% on a scale >15 mmol that can provide multiple grams of the three-component product.
- Carosi, Lisa,Hall, Dennis G.
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experimental part
p. 650 - 661
(2009/10/30)
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- Copper catalyzed asymmetric synthesis of chiral allylic esters
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The complex derived from Taniaphos ligand 4 and CuBr?Me2S catalyzes the asymmetric addition of Grignard reagents to 3-bromopropenyl esters 1 to provide allylic esters 2 in high yields and high chemio-, regio-, and enantioselectivities. The work demonstrates that allylic asymmetric alkylation (AAA) can be done on substrates bearing a heteroatom at the γ-position. The method is a practical route to chiral, nonracemic allylic alcohols. The use of functionalized substrates 1 or Grignard reagents leads to more complex products 2, which can be further manipulated as demonstrated in conversion to (S)-5-ethyl-2(5H)-furanone 6 and (S)-benzoic acid-cyclopent-2-enyl ester 7. Copyright
- Geurts, Koen,Fletcher, Stephen P.,Feringa, Ben L.
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p. 15572 - 15573
(2007/10/03)
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- Mechanistic implications of nickel-catalyzed reductive coupling of aldehydes and chiral 1,6-enynes
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A study of nickel-catalyzed reductive coupling reactions of aldehydes and chiral 1,6-enynes has provided evidence for three distinct mechanistic pathways that govern regioselectivity in this transformation. In the absence of a phosphine additive, high regioselectivity and high diastereoselectivity are obtained as a direct result of coordination of both the alkyne and the olefin to the metal center during the C-C bond-forming step.
- Moslin, Ryan M.,Jamison, Timothy F.
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p. 455 - 458
(2007/10/03)
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- Directing effects of tethered alkenes in nickel-catalyzed coupling reactions of 1,6-enynes and aldehydes
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Nickel-catalyzed reductive coupling reactions of aldehydes and 1,6-enynes proceed in excellent regioselectivity in the absence of a phosphine, and the use of a monodentate phosphine additive leads to the formation of the opposite regioisomer with equally high selectivity. Both products are the result of the same fundamental mechanism, with the inversion of regioselectivity being the result of stereospecific ligand substitution at the metal center.
- Moslin, Ryan M.,Miller, Karen M.,Jamison, Timothy F.
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p. 7598 - 7610
(2007/10/03)
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- Synthesis and SAR studies of 3-phenoxypropyl piperidine analogues as ORL1 (NOP) receptor agonists
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A series of 3-phenoxypropyl piperidine analogues have been discovered as novel ORL1 receptor agonists. Structure-activity relationships have been explored around the 3-phenoxypropyl region with several potent and selective analogues identified.
- Palin, Ronald,Barn, David R.,Clark, John K.,Cottney, Jean E.,Cowley, Phillip M.,Crockatt, Marc,Evans, Louise,Feilden, Helen,Goodwin, Richard R.,Griekspoor, Frank,Grove, Simon J.A.,Houghton, Andrea K.,Jones, Philip S.,Morphy, Richard J.,Smith, Alasdair R.C.,Sundaram, Hardy,Vrolijk, David,Weston, Mark A.,Wishart, Grant,Wren, Paul
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p. 589 - 593
(2007/10/03)
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- Liquid-phase isomerization of saturated and unsaturated epoxides
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The liquid-phase isomerization of a variety of epoxides was studied using a complex catalyst system based on magnesium bromide and dimethylformamide. The data obtained elucidate the mechanism of the liquid-phase isomerization and show the range of oxygen-containing compounds which can be prepared through this reaction.
- Mel'nik,Khvatova,Moskvichev,Srednev,Egorova
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p. 167 - 169
(2007/10/03)
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- Isomerization of allylic silyl ethers catalyzed by ReO3(OSiR3) complexes
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Efficient isomerization of allylic alcohols and allylic ethers at room temperature by rhenium (VII) oxo complexes is described. (C) 2000 Elsevier Science Ltd.
- Bellemin-Laponnaz, Stéphane,Le Ny, Jean Pierre,Osborn, John A.
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p. 1549 - 1552
(2007/10/03)
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- Silicon-directed acid ring-opening of allyltrimethylsilane oxide. X-ray structures of 3-triisopropylsilyl-2-(2,4-dinitrobenzoyloxy)-1-propanol and 3-triisopropylsilyl-2-(2,4,6-trinitrobenzoyloxy)-1-propanol
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Allyltrimethylsilane oxide 5 undergoes regiospecific ring-opening with carboxylic acids in chloroform to give the hydroxy esters 6a-e. In polar solvents competing elimination results in the formation of allyl alcohol. Allyltriisopropylsilane oxide 17 undergoes analogous reactions as 5 in chloroform but does not undergo elimination in methanol or acetone. The X-ray structures of 18b and 18c reveal significant lengthening of the C-O (ester) bond (a remarkable 1.502(2) A for 18c), these structural effects are due to strong σC-Si-σ*C-O interactions, particularly for 18c.
- Badali, Fatmir,Issa, William,Pool, Brett,White, Jonathan M.
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p. 251 - 260
(2007/10/03)
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- Palladium(II)-Catalyzed Intramolecular Aminocarbonylation of endo-Carbamates under Wacker-Type Conditions
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Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typical conditions: acidic conditions [conditions A, typically PdCl2 (0.1 equiv) and CuCl2 (3.0 equiv) under 1 atm of CO at room temperature in methanol] and buffered conditions [conditions B, typically PdCl2 (0.1 equiv) and CuCl2 (2.3 equiv) under 1 atm of CO at 30°C in trimethyl orthoacetate]. Among nitrogen nucleophiles, endocarbamates 7 display distinctive reactivity: endo-carbamates 7a-k smoothly undergo intramolecular aminocarbonylation under conditions B to furnish 4-[(methoxycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they would not undergo the expected reaction under conditions A. Other nitrogen nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-tosylamides 9), on the other hand, satisfactorily undergo aminocarbonylation only under conditions A to give rise to 2,4,6, and 10, respectively, in good yields. Under conditions B, they are unreactive and provide either the expected products in poor yields or intractable mixtures of products. On the basis of this contrasting reactivity between endo-carbamates and other nitrogen nucleophiles, the chemoselective aminocarbonylation of 71-o has been achieved; aminocarbonylation takes place at the endo-carbamate moieties to furnish 81-o exclusively under conditions B, and aminocarbonylation occurs at the exo-carbamate, exo-urea, and exo-tosylamide moieties to yield 13a-d exclusively under conditions A.
- Harayama, Hiroto,Abe, Atsuhiro,Sakado, Tomonori,Kimura, Masanari,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao
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p. 2113 - 2122
(2007/10/03)
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- Pheromones of insects and their analogs. LIV. Synthesis of dodec-9e-en-1-ol and its acetate - Components of the sex pheromone of Sparganothis pilleriana
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Using the Claisen rearrangement in the construction of a double bond with the E configuration, we have synthesized dodec-9E-en-1-ol and its acetate, which are components of the sex pheromone of Sparganothis pilleriana.
- Odinokov,Vakhidov,Shakhmaev,Zorin
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p. 912 - 914
(2007/10/03)
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- Gas-Phase Protonation of Spiropentane. A Novel Entry into the C5H9+ Potential Energy Surface
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The structures, stabilities, and isomerization patterns of C5H9+ ions arising from the gas-phase protonation of spiropentane have been investigated by nuclear-decay, radiolytic, and FT-ICR techniques combined with ab initio calculations.The experimental and theoretical results are consistent with the initial formation of a corner-protonated spiropentane intermediate 17, whose lifetime in the gas phase exceeds 7E-9 s.This local C5H9+ minimum is separated from ca. 30 kcal mol-1 more stable cyclopentyl cation as well as from dimethylallyl open-chain isomers by significant energy barriers.Persistency of 17 in the gas phase does not find any correspondence in solution.Solvation and ion-pairing effects may explain the failure to detect C5H9+ structures retaining the spirobicyclic framework of spiropentane in the condensed phase.
- Cecchi, Patrizio,Pizzabiocca, Adriano,Renzi, Gabriele,Grandinetti, Felice,Sparapani, Cinzia,et al.
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p. 10338 - 10347
(2007/10/02)
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- Preparation of β, γ-unsaturated carboxylic acids
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β, γ-Unsaturated carboxylic acids, e.g., 3-hexene-1,6-dioic acid, are selectively prepared by carbonylating (with carbon monoxide) an allyl alcohol, e.g., a butenediol, at an elevated temperature and under superatmospheric pressure, in the presence of a catalytically effective amount of a palladium-based catalyst and at least one quaternary onium chloride of one of the Group VB elements nitrogen or phosphorus, such element being tetracoordinated via carbon atoms and with the proviso that such nitrogen atom may be coordinated to two pentavalent phosphorus atoms.
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- An Efficiente Preperation of Optically Active Allylic Alcohols, 2-Furyl Alcohols and 2-Thienyl Alcohols by Catalytic Asymmetric Alkylation
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Highly enantioselective alkylation of some kinds of α,β-unsaturated aldehydes with dialkylzinc proceed in the presence of a small amount of a chiral β-amino alcohol, thus providing an efficient method of obtaining optically active secondary allylic alcohols.Optically active 2-furyl and 2-thienyl alcohols are also available by this catalytic asymmetric alkylation method.
- Hayashi, Masahiko,Kaneko, Toshiyuki,Oguni, Nobuki
-
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- Asymmetric Hetero-Diels-Alder Reaction of α-Alkoxy Aldehydes with Activated Dienes. The Scope of Lewis Acid Chelation-Controlled Cycloadditions
-
The cycloaddition reactions of various α-alkoxy aldehydes with 1,3-dimethoxy-1--1,3-butadiene (Brassard's diene, 2) were performed under the Lewis acid catalysis of Eu(hfc)3, magnesium dibromide, or diethylaluminum chloride.Moderate to high diastereoselectivities were observed with Eu(hfc)3 and magnesium dibromide.Evidence from reactions of Eu(hfc)3 and magnesium dibromide catalysis indicated a possible "chelation-control" pathway.Lewis acid catalysis from diethylaluminum chloride provides products with moderate to high diastereoselectivity.The mechanistic pathway with catalysis by diethylaluminum chloride was less clear.A possible mechanism based upon a "Cram" addition is considered.
- Midland, M. Mark,Koops, Roger W.
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p. 5058 - 5065
(2007/10/02)
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- Intramolecular Activation of a N-Methyl C-H Bond by an Electron Rich Iridium Centre: a Novel Chemoselective Reduction Catalyst
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The iridium complex > formed by intramolecular C-H oxidative addition, as shown by X-ray analysis, behaves as a chemoselective catalyst in hydrogen transfer reduction of α,β-unsaturated ketones to unsaturated alcohols.
- Farnetti, Erica,Nardin, Giorgio,Graziani, Mauro
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p. 1264 - 1265
(2007/10/02)
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- A MEERWEIN-PONNDORF-VERLEY TYPE REDUCTION OF α,β UNSATURATED KETONES TO ALLYLIC ALCOHOLS CATALYZED BY MgO
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Allylic alcohols are obtained with an unprecedented simple method by chemoselective hydrogen transfer reduction of α,β unsaturated ketones catalyzed by MgO.
- Kaspar, J.,Trovarelli, A.,Lenarda, M.,Graziani, M.
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p. 2705 - 2706
(2007/10/02)
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- Continuous preparation of aldehydes and ketones
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Aldehydes and ketones of the general formula I STR1 where R1 is hydrogen or an organic radical of 1 to n carbon atoms and R2 is a non-aromatic organic radical of 1 to m carbon atoms, (m+n) ranging from 2 to 24 and R1 and R2 being combinable to form a 4- to 12-membered ring, are prepared in a continuous manner by oxidizing an alcohol of the general formula II STR2 with oxygen or an oxygen-containing gas at elevated temperatures in the gas phase in the presence of a catalyst, by effecting the oxidation by means of a supported catalyst composed of an inert carrier having a smooth surface and from 0.1 to 20% by weight, based on the amount of carrier, of an active layer of copper, silver and/or gold in a tubular reactor or tube bundle reactor where the internal diameter D of the tube or tubes ranges from 10 to 50 mm and the largest diameter d of the coated supported catalysts is subject to the relationship d=from 0.1 to 0.2 D.
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- SELECTIVE REDUCTION OF α,β-UNSATURATED KETONES WITH POTASSIUM TRIPHENYLBOROHYDRIDE
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Potassium triphenylborohydride is an excellent 1,4-reducing agent for acyclic enones and β-unsubstituted cyclohexenones, and shows a greater tendency for 1,4-reduction than K-Selectride for β-substituted cyclohexenones and aromatic enones.
- Kim, Kwan Eung,Park, Soo Bong,Yoon, Nung Min
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- Studies on the Addition of Allyl Oxides to Sulfonylallenes. Preparation of Highly Substituted Allyl Vinyl Ethers for Carbanionic Claisen Rearrangements
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Thirty-five allyl vinyl ethers bearing an arylsulfonyl anion-stabilizing group have been prepared by addition of allylic alkoxides to (arylsulfonyl)allenes.The allyl vinyl ethers are produced as either β,γ-unsaturated or α,β-unsaturated sulfones depending upon the substitution pattern of the allene and the reaction conditions.A wide variety of substitution patterns are available by using this method.Factors that control the position and stereochemistry of the vinyl ether double bond are discussed.
- Denmark, Scott E.,Harmata, Michael A.,White, Kathleen S.
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p. 4031 - 4042
(2007/10/02)
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- Convenient deuterium labeling on a gas-liquid chromatography column. Preparative scale formation of α,β-unsaturated Od-alcohols
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Several α,β-unsaturated ethylenic and acetylenic alcohols 1-11 were conveniently deuterated on oxygen, by a GLC technique, with high yields and 80 to 98percent deuterium incorporation.
- Georgoulis, Constantin,Smadja, William,Ville, Guy
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p. 269 - 270
(2007/10/02)
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- INTRODUCTION OF CENTER OF CHIRALITY INTO FLUOROCOMPOUNDS BY MICROBIAL TRANSFORMATION OF 2,2,2-TRIFLUOROETHANOL
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2,2,2-Trifluoroethanol is found to be a valuable synthetic tool proceeding to the chiral trifluoromethylated compounds via enantiotopic differentiating reaction and carbon-carbon bond formation with active fermenting baker's yeast.
- Kitazume, Tomoya,Ishikawa, Nobuo
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p. 1815 - 1818
(2007/10/02)
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- Metastable Decompositions of C5H10O+. Ions with the Oxygen on the Middle Carbon: A Test for Energy Randomization
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This study was undertaken to define the mechanisms of metastable decomposition of C5H10O+. ions with the oxygen on the middle carbon, and to test the assumption that internal energy becomes randomly distributed prior to the unimolecular decompositions of gaseous ions.CH3CH2C(=OH+)CH2CH2. (2), CH3CH2C(=OH+).CHCH3 (3), and CH3CH2C(OH+.)HCH=CH2 (4) all rearrange to CH3CH2C(=O+.)CH2CH3 (1) prior to metastable decomposition.However, 2 - 4 lose ethyl 50 - 100 times as often as they lose ethane following rearrangement to 1, while 1 formed by ionization of 3-pentanone loses exclusively ethane.These differences are attributed to excess energy in the isomerized ions. 3-Pentanone ions formed by isomerization of 2 - 4 lose ethyl and ethane from opposite sides at unequal rates, possibly owing to incomplete randomization of energy following isomerization.
- McAdoo, David J.,Farr, William,Hudson, Charles E.
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p. 5165 - 5169
(2007/10/02)
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- Synthesis of (E)-6-Nonen-1-ol, a Sex Pheromone of Male Fruit Fly Ceratitis capitata Wiedemann
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(E)-6-Nonen-1-ol (I) has been synthesised starting from propenal.Grignard reaction of ethylmagnesium bromide on propenal gives the allylic alcohol (II) which on mercuric acetate catalysed trans-etherification with ethyl vinyl ether yields the allyl vinyl ether (III).Claisen migration of III provides (E)-4-hepten-1-al (VI) which is smoothly reduced with LAH to the alcohol (V).Conversion of V into the corresponding mesylate (Va), followed by alkylation with ethyl malonate furnishes the diester (VI) which when decarbethoxylated with NaCl/DMSO yields ethyl (E)-6-nonenoate (VII).LAH reduction of VII results in the formation of the title compound (I).
- Vig, O. P.,Sharma, M. L.,Gakhar, Madhu,Malik, Neera
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p. 356 - 357
(2007/10/02)
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- Condensation de reactifs organomagnesiens sur les bromhydrines du type R-CH(Br)-CH2OH. Influence des sels cuivreux.
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Various allylic, vinylic and arylic Grignard reagents are able to condense with 2-bromo-1-alkanols in THF.The catalytic use of copper salts diminishes side reactions but is not required.
- Bourgain-Commercon, Monique,Normant, Jean F.
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p. 289 - 294
(2007/10/02)
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