- Ligand-controlled cobalt-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes
-
The Co-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes were realized by a ligand-controlled strategy. The remote hydroboration with dcype provided borylethers, while xantphos favored the formation of silyl enol ethers.
- Huang, Jiaxin,Li, Jie,Yang, Wen,Zhang, Kezhuo,Zhao, Pei,Zhao, Wanxiang
-
supporting information
p. 302 - 305
(2022/01/03)
-
- Highly Regioselective 5-endo-tet Cyclization of 3,4-Epoxy Amines into 3-Hydroxypyrrolidines Catalyzed by La(OTf)3
-
Highly regioselective intramolecular aminolysis of 3,4-epoxy amines has been achieved. Key features of this reaction are (1) chemoselective activation of epoxides in the presence of unprotected aliphatic amines in the same molecules by a La(OTf)3 catalyst and (2) excellent regioselectivity for anti-Baldwin 5-endo-tet cyclization. This reaction affords 3-hydroxy-2-alkylpyrrolidines stereospecifically in high yields. DFT calculations revealed that the regioselectivity might be attributed to distortion energies of epoxy amine substrates. The use of this reaction was demonstrated by the first enantioselective synthesis of an antispasmodic agent prifinium bromide.
- Hoshino, Yoshihiko,Iwabuchi, Yoshiharu,Kuriyama, Yuse,Sasano, Yusuke,Uesugi, Shun-ichiro,Yamaichi, Aoto
-
supporting information
p. 1961 - 1965
(2021/01/04)
-
- MIXTURE OF 3-HEXEN-1-OL ISOMERS AND A PROCESS OF PREPARING SAME
-
Compositions comprising 3-hexen-l-ol are described herein, as well as odor-imparting formulations comprising same and articles-of-manufacturing comprising such compositions or odor-imparting formulations. The compositions comprise trans- 3-hexen-l-ol in a range of from 67 % to 82 % by weight and cA-3-hexen-l-ol in a range of from 18 % to 33 % by weight, wherein a total concentration of trans- 3-hexen-l-ol and cA-3-hexen-l-ol is at least 97 % by weight. Further described herein is a process for preparing a composition comprising 3-hexen-l-ol, the process comprising: contacting 1-pentene with a formaldehyde in the presence of a Lewis acid to thereby obtain a crude mixture comprising 3-hexen-l-ol; and contacting the mixture comprising 3-hexen- l-ol with a base.
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-
Page/Page column 21-22
(2021/08/14)
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- ENVIRONMENTALLY-FRIENDLY HYDROAZIDATION OF OLEFINS
-
The present invention provides processes for the synthesis of organic azides, intermediates for the production thereof, and compositions related thereto.
- -
-
Page/Page column 97-98
(2020/01/24)
-
- Tandem IBX-Promoted Primary Alcohol Oxidation/Opening of Intermediate β,γ-Diolcarbonate Aldehydes to (E)-γ-Hydroxy-α,β-enals
-
A tandem IBX-promoted oxidation of primary alcohol to aldehyde and opening of intermediate β,γ-diolcarbonate aldehyde to (E)-γ-hydroxy-α,β-enal has been developed. Remarkably, the carbonate opening delivered exclusively (E)-olefin and no over-oxidation of γ-hydroxy was observed. The method developed has been extended to complete the stereoselective total synthesis of both (S)- and (R)-coriolides and d-xylo- and d-arabino-C-20 guggultetrols.
- Kumari, Anupama,Gholap, Sachin P.,Fernandes, Rodney A.
-
p. 2278 - 2290
(2019/06/17)
-
- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
-
A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
-
supporting information
p. 8321 - 8331
(2019/06/04)
-
- Catalytic Regio- and Enantioselective Oxytrifluoromethylthiolation of Aliphatic Internal Alkenes by Neighboring Group Assistance
-
Chiral selenide-catalyzed oxytrifluoromethylthiolation of aliphatic internal alkenes by a formally intermolecular strategy is disclosed, affording CF3S 1,3-amino alcohol and 1,3-diol derivatives with high regio-, enantio-, and diastereoselectivities. The reactions are promoted by a neighboring imide or ester group on substrates via a six-membered ring transition state. This assistance strategy is also successfully applied to the regio- and diastereoselective oxyhalofunctionalization of internal alkenes and the conversion of alkynes.
- Xu, Jia,Zhang, Yuanyuan,Qin, Tian,Zhao, Xiaodan
-
supporting information
p. 6384 - 6388
(2018/10/09)
-
- Iron-Catalyzed Direct Olefin Diazidation via Peroxyester Activation Promoted by Nitrogen-Based Ligands
-
We herein report an iron-catalyzed direct diazidation method via activation of bench-stable peroxyesters promoted by nitrogen-based ligands. This method is effective for a broad range of olefins and N-heterocycles, including those that are difficult substrates for the existing olefin diamination and diazidation methods. Notably, nearly a stoichiometric amount of oxidant and TMSN3 are sufficient for high-yielding diazidation for most substrates. Preliminary mechanistic studies elucidated the similarities and differences between this method and the benziodoxole-based olefin diazidation method previously developed by us. This method effectively addresses the limitations of the existing olefin diazidation methods. Most notably, previously problematic nonproductive oxidant decomposition can be minimized. Furthermore, X-ray crystallographic studies suggest that an iron-azide-ligand complex can be generated in situ from an iron acetate precatalyst and that it may facilitate peroxyester activation and the rate-determining C-N3 bond formation during diazidation of unstrained olefins.
- Shen, Shou-Jie,Zhu, Cheng-Liang,Lu, Deng-Fu,Xu, Hao
-
p. 4473 - 4482
(2018/05/22)
-
- Gold-Ligand-Catalyzed Selective Hydrogenation of Alkynes into cis-Alkenes via H2 Heterolytic Activation by Frustrated Lewis Pairs
-
The selective hydrogenation of alkynes to alkenes is an important synthetic process in the chemical industry. It is commonly accomplished using palladium catalysts that contain surface modifiers, such as lead and silver. Here we report that the adsorption of nitrogen-containing bases on gold nanoparticles results in a frustrated Lewis pair interface that activates H2 heterolytically, allowing an unexpectedly high hydrogenation activity. The so-formed tight-ion pair can be selectively transferred to an alkyne, leading to a cis isomer; this behavior is controlled by electrostatic interactions. Activity correlates with H2 dissociation energy, which depends on the basicity of the ligand and its reorganization on activation of hydrogen. High surface occupation and strong Au atom-ligand interactions might affect the accessibility and stability of the active site, making the activity prediction a multiparameter function. The promotional effect found for nitrogen-containing bases with two heteroatoms was mechanistically described as a strategy to boost gold activity. (Graph Presented).
- Fiorio, Jhonatan L.,López, Núria,Rossi, Liane M.
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p. 2973 - 2980
(2017/05/31)
-
- Selective hydrogenation of 3-Hexyn-1-ol with Pd nanoparticles synthesized via microemulsions
-
In the study at hand we present a design strategy for novel catalysts which can be used for the selective hydrogenation of alkynes to alkenes. The design of the novel catalysts is based on two main ideas, namely (1) the synthesis of Pd nanoparticles via microemulsions and (2) the use of highly-ordered mesoporous silica with a 3-D pore network (FDU-12) serving as support. The nanoparticles are deposited on FDU-12 in two different ways. Firstly, we simply impregnated the support with a dispersion of the nanoparticles. The resulting catalyst was not selective at all; on the contrary, it fully hydrogenated our model alkyne, namely 3-hexyn-1-ol. Secondly, we synthesized the FDU-12 in the presence of the nanoparticles (in-situ synthesis). In this case, we obtained one catalyst which performed as well as the Lindlar catalyst although the metal content was slightly lower and our catalyst contained no Pb. Another catalyst of the same series, prepared in the presence of another stabilizer, performed as well as the NanoSelect catalyst but at a 7 times higher metal content. For the sake of comparison we also impregnated FDU-12 via classical incipient wetness impregnation and again obtained a completely nonselective catalyst. Our results demonstrate that the in-situ synthesis has great potential as regards the development of novel catalysts.
- Montsch, Thomas,Heuchel, Moritz,Traa, Yvonne,Klemm, Elias,Stubenrauch, Cosima
-
-
- Unconventional Pd@Sulfonated Silica Monoliths Catalysts for Selective Partial Hydrogenation Reactions under Continuous Flow
-
Doubly functionalized, hierarchical-porosity silica monoliths were synthesized by postgrafting of sulfonic groups and in situ growth of Pd nanoparticles in that order. PdNP of 3.1 nm size located in the mesopores of the material showed to be evenly distributed within 4.6 % wt Pd monoliths. The system was explored in the continuous-flow, catalytic partial hydrogenation reaction of 3-halogeno-nitrobenzenes and 3-hexyn-1-ol in the liquid phase, showing remarkable conversion, selectivity, and resistance under very mild conditions.
- Liguori, Francesca,Barbaro, Pierluigi,Said, Bilel,Galarneau, Anne,Santo, Vladimiro Dal,Passaglia, Elisa,Feis, Alessandro
-
p. 3245 - 3258
(2017/08/29)
-
- PdNP@Titanate Nanotubes as Effective Catalyst for Continuous-Flow Partial Hydrogenation Reactions
-
Pd nanoparticles were easily immobilized onto titanate nanotubes by a straightforward procedure. The material (0.50 wt % Pd) was used as catalyst in the continuous-flow, liquid-phase hydrogenation reaction of unsaturated C-C bonds and it showed excellent performance and durability under very mild conditions (room temperature, 1-2 bar H2, residence time 13-36 s). In particular, very high productivity was obtained in the synthesis of the perfumery component cis-3-hexen-1-ol (40.6 mol gPd-1 h-1) without additives or metal contamination, with clear benefits in terms of process economy and environmental impact compared with conventional catalysts. The catalyst performance is discussed in the light of comparable systems.
- Linares, Noemi,Moreno-Marrodan, Carmen,Barbaro, Pierluigi
-
p. 1001 - 1011
(2016/03/15)
-
- Synthesis of bicyclic tetrahydrofurans from linear precursors using manganese(III) acetate
-
We have recently developed methodology based on oxidative radical reactions for the synthesis of [3.3.0]-bicyclic lactones containing both cyclopentanes and γ-lactams along with application of this methodology to the synthesis of natural products and complex molecular architectures. Herein we report an extension of this methodology to the synthesis of oxygen heterocycles including bicyclic bis-lactones.
- Chany, Anne-Caroline,Marx, Léo B.,Burton, Jonathan W.
-
supporting information
p. 9190 - 9193
(2015/09/07)
-
- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
-
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.
- -
-
-
- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
-
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.
- -
-
-
- Control of the selectivity in multi-functional group molecules using supported gold-palladium nanoparticles
-
The oxidation of 2-hexen-1-ol and 1-hexen-3-ol with air has been studied using supported gold, palladium and gold-palladium catalysts. The main aim was to determine if either the alcohol or alkene functional group can be oxidised selectively. However, based on the reaction products observed (2-hexen-1-ol forms 2-hexene, hexanal, (E)-2-hexenal, (E)-3-hexen-1-ol, 4-hexen-1-ol and (E)-2-hexanoic acid. 1-Hexen-3-ol forms 1-hexene, 3-hexanone, 1-hexen-3-one and 3-hexenol), the main pathway in these reactions is isomerisation and, in addition, significant yields of the products are due to a disproportionation reaction. Controlling the selectivity in molecules with multiple function groups by manipulating the catalyst composition and reaction conditions can promote or hinder the various reaction pathways, thereby increasing the selectivity to the desired oxidation products.
- Alshammari, Hamed,Miedziak, Peter J.,Morgan, David J.,Knight, David W.,Hutchings, Graham J.
-
p. 1244 - 1254
(2013/06/26)
-
- SUPPORTED METAL CATALYSTS
-
The present invention relates to supported metal catalysts, wherein the catalysts are modified by at least one amine, a method for the preparation thereof and hydrogenation processes utilising the supported metal catalysts.
- -
-
Paragraph 0280
(2013/03/28)
-
- A well-defined Pd hybrid material for the Z-selective semihydrogenation of alkynes characterized at the molecular level by DNP SENS
-
Direct evidence of the conformation of a Pd-N heterocyclic carbene (NHC) moiety imbedded in a hybrid material and of the Pd-NHC bond were obtained by dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) at natural abundance in short experimental times (hours). Overall, this silica-based hybrid material containing well-defined Pd-NHC sites in a uniform environment displays high activity and selectivity in the semihydrogenation of alkynes into Z-alkenes (see figure). Copyright
- Conley, Matthew P.,Drost, Ruben M.,Baffert, Mathieu,Gajan, David,Elsevier, Cornelis,Franks, W. Trent,Oschkinat, Hartmut,Veyre, Laurent,Zagdoun, Alexandre,Rossini, Aaron,Lelli, Moreno,Lesage, Anne,Casano, Gilles,Ouari, Olivier,Tordo, Paul,Emsley, Lyndon,Coperet, Christophe,Thieuleux, Chloe
-
supporting information
p. 12234 - 12238
(2013/09/23)
-
- New environmentally friendly catalysts containing Pd-interstitial carbon made from Pd-glucose precursors for ultraselective hydrogenations in the liquid phase
-
We report a novel preparation of a Pd nanocatalyst modified with subsurface C via blending a glucose precursor at the molecular level: the catalyst is demonstrated for the first time to be stereoselective in the hydrogenation of alkynes to cis-alkenes in the liquid phase.
- Chan, Chun Wong Aaron,Xie, Yaling,Cailuo, Nick,Yu, Kai Man Kerry,Cookson, James,Bishop, Peter,Tsang, Shik Chi
-
supporting information; scheme or table
p. 7971 - 7973
(2011/08/07)
-
- Stereoselective hydrogenation of olefins using rhodium-substituted carbonic anhydrase - A new reductase
-
One useful synthetic reaction missing from nature's toolbox is the direct hydrogenation of substrates using hydrogen. Instead nature uses co-factors like NADH to reduce organic substrates, which adds complexity and cost to these reductions. To create an enzyme that can directly reduce organic substrates with hydrogen, researchers have combined metal hydrogenation catalysts with proteins. One approach is an indirect link where a ligand is linked to a protein and the metal binds to the ligand. Another approach is direct linking of the metal to protein, but nonspecific binding of the metal limits this approach. Herein, we report a direct hydrogenation of olefins catalyzed by rhodium(I) bound to carbonic anhydrase (CA-[Rh]). We minimized nonspecific binding of rhodium by replacing histidine residues on the protein surface using site-directed mutagenesis or by chemically modifying the histidine residues. Hydrogenation catalyzed by CA-[Rh] is slightly slower than for uncomplexed rhodium(I), but the protein environment induces stereoselectivity favoring cis- over transstilbene by about 20:1. This enzyme is the first cofactor-independent reductase that reduces organic molecules using hydrogen. This catalyst is a good starting point to create variants with tailored reactivity and selectivity. This strategy to insert transition metals in the active site of metalloenzymes opens opportunities to a wider range of enzyme-catalyzed reactions.
- Jing, Qing,Okrasa, Krzysztof,Kazlauskas, Romas J.
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supporting information; scheme or table
p. 1370 - 1376
(2009/09/04)
-
- 1,4-HYDROGENATION OF DIENES WITH RU COMPLEXES
-
The present invention relates to the use of Ru complexes, having a cyclopentadienyl derivatives and a diene as ligands, together with some acidic additives for improving the selectivity in the 1,4-hydrogenation of conjugated dienes into the corresponding "cis "-alkene as major product, i.e. wherein the two substituents in position 2,3 of said diene are in a cis configuration in the corresponding alkene.
- -
-
Page/Page column 19; 23-24
(2008/12/04)
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- 1,4-HYDROGENATION OF SORBOL WITH RU COMPLEXES
-
The present invention relates to the use of Ru complexes, having a pentamethyl- cyclopentadienyl and a cyclooctadine as ligands, together with some acidic additives for improving the selectivity in the 1,4-hydrogenation of sorbol into the corresponding Z-alkene as major product.
- -
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Page/Page column 7-9
(2008/12/04)
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- Process for preparing cis alkenes and new catalysts therefor
-
In a method for preparation of cis-alkenes (I) by hydrogenating conjugated, non-cyclic dienes (II) in presence of homogeneously soluble transition metal catalyst (III), the new feature is that (III) is prepared in situ. In a method for preparation of cis-alkenes (I) by hydrogenating conjugated, non-cyclic dienes (II) in presence of homogeneously soluble transition metal catalyst (III), the new feature is that (III) is prepared in situ. (III) are of formulae (IIIa) or (IIIb). M = in (IIIa), a transition metal of Group VI in zero oxidation state, or in (IIIb) a metal of Group VIII in +2 oxidation state, Group IX in +1 oxidation state or Group X in +2 oxidation state; L1 = polydentate neutral or anionic ligand; L2 and L3 = together a conjugated, non-cyclic diene ligand; L4 = monodentate neutral ligand; L5 = polydentate neutral ligand; X = anion; and n = 1 or 2. Independent claims are also included for the following: (1) transition metal complex (C) for stereoselective hydrogenation of conjugated dienes to cisoid compounds that comprises a central ruthenium(II), an eta5 ligand, a bidentate, non-cyclic conjugated diene ligand and optionally a non-coordinating counterion for electrical neutrality, provided that when the ligand is pentamethylcyclopentadienyl (CpMe5) and the diene is sorbic acid, then the counterion is not triflate (trifluoromethylsulfonate) nor the BARF anion; and (2) methods for preparing specific (C).
- -
-
Page/Page column 10
(2010/02/05)
-
- First example of high loaded polymer-stabilized nanoclusters immobilized on hydrotalcite: Effects in alkyne hydrogenation
-
Poly(N-vinyl-2-pyrrolidone)-stabilized Pd-nanoclusters, for the first time exclusively supported on the hydrotalcite lateral surface, showed a remarkable catalytic performance in the selective hydrogenation of 3-hexyn-1-ol, which can be ascribed to both the influence of the protecting polymer PVP as well as the nature of the support.
- Roelofs, Jules C. A. A.,Berben, Peter H.
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p. 970 - 971
(2007/10/03)
-
- Deprotection of benzyl and p-methoxybenzyl ethers by chlorosulfonyl isocyanate-sodium hydroxide
-
CSI-NaOH procedure provided a new and mild methodology for the deprotection of benzyl and p-methoxybenzyl ethers without affecting the other functional groups under similar reaction conditions.
- Kim, Ji Duck,Han, Gyoonhee,Zee, Ok Pyo,Jung, Young Hoon
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p. 733 - 735
(2007/10/03)
-
- Serine carbonates
-
Serine carbonates of formula I are precursors for organoleptic compounds, masking agents and antimicrobial agents. Further they are alternative substrates for malodor producing enzymes. The symbols in formula I are defined in claim 1.
- -
-
-
- Compounds having protected hydroxy groups
-
The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
- -
-
-
- Compounds having protected hydroxy groups
-
The present invention relates to compounds with protected hydroxy groups of formula (I) These compounds are precursors for organoleptic agents, such as fragrances, and masking agents and for antimicrobial agents. When activated, the compounds of formula (I) are cleaved and form one or more organoleptic and/or antimicrobial compounds.
- -
-
-
- In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to (E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst
-
The hydrogenation of internal alkynes using a [Cp*Ru(alkene)]+ complex leads to the formation of (E)-alkenes. This ruthenium complex represents one of the few homogeneous catalysts that trans-hydrogenate internal alkynes directly and stereoselectively. We have studied its stereoselectivity by in situ PHIP-NMR spectroscopy (PHIP = para-hydrogen induced polarization). With this method the initially formed products can be identified and characterized even at very low concentrations and low conversions. Furthermore, their subsequent fate can be evaluated with high sensitivity and with time resolution. Different alkyne substrates were used to demonstrate the universal applicability of this catalyst. The catalyst is not active in combination with terminal alkynes, however, possibly due to the formation of a rather stable vinylidene complex. A mechanism proceeding via a binuclear complex is proposed to explain the formation of the (E)-alkenes.
- Schleyer,Niessen,Bargon
-
p. 423 - 426
(2007/10/03)
-
- Beta-ketoester compounds
-
The beta-ketoesters of formula I are useful as precursors for organoleptic compounds, especially for flavors, fragrances and masking agents and antimicrobial compounds.
- -
-
-
- Ketone precursors for organoleptic compounds
-
The invention discloses ketones of formula I: wherein, Y is an optionally substituted alkyl, cycloalkyl, or cycloalkylalkyl, wherein each alkyl group is straight or branched and each alkyl and cycloalkyl group is saturated or unsaturated; R1is hydrogen or a C1-6alkyl group that is substituted, saturated or unsaturated, straight or branched; A is a chromophoric substituted aromatic ring or ring system; n is an integer; and with the proviso that formula I is not 2-ethoxy-1-phenyl-ethanone. These compositions are useful for the delivery of organoleptic compounds, especially of flavors, fragrances, masking agents and antimicrobial compounds.
- -
-
-
- A new, highly stereoselective approach to pyrrolidines via overall 5-endo-trig cyclisations of homoallylic tosylamides
-
Iodocyclisations of E-homoallylic tosylamides 7 lead to excellent yields of either 2,5-trans- or 2,5-cis-3-iodopyrrolidines (10 or 11), depending upon the reaction conditions.
- Jones, Andrew D.,Knight, David W.
-
p. 915 - 916
(2007/10/03)
-
- Benzotriazole-mediated [2,3]-wittig rearrangement. General and stereocontrolled syntheses of homoallyl alcohols and β,γ-unsaturated ketones
-
Readily accessible allyl 1-(benzotriazol-1-yl)alkyl ethers (13 and 19), upon treatment with 2.5 equiv of nucleophilic lithium reagents, give secondary and tertiary homoallyl alcohols (16 and 21), respectively, exclusively in the E configuration in excellent yields. This is achieved by deprotonation followed by [2,3]-Wittig rearrangement, departure of the benzotriazolyl group, and then nucleophilic addition to the resulting carbonyl compound. Following a similar protocol, primary E-homoallyl alcohols 18 are prepared in good yield by the reaction of ethers 13 with LDA in the presence of NaBH4. Our approach complements the stereochemical Z-selective syntheses of primary homoallyl alcohols of Still and of Bruckner. Wittig rearrangement of the anions of 19 generated with LDA analogously furnishes E-β,γ-unsaturated ketones 20 in excellent yields.
- Katritzky, Alan R.,Wu, Hong,Xie, Linghong
-
p. 4035 - 4039
(2007/10/03)
-
- COMPOUNDS WITH A HERBAL ODOR VI. THE E ISOMERS OF THE STRUCTURAL ANALOGS OF LEAF ALCOHOL
-
The E isomers of leaf alcohol and its structural analogs differing in the length of the carbon chain, the presence of substituents at various positions of the molecule, the position of the double bond, and replacement of the double bond by a three-membered ring were synthesized.Many representatives of the Z and E series have a herbal odor, and similarity is observed in the odor of the respective pairs of Z and E isomers.The proximity of the odor of the investigated compounds to the standard (leaf alcohol) is determined by the number of carbon atoms in their molecules.
- Vasil'ev, A. A.,Cherkaev, G. V.,Nikitina, M. A.
-
p. 870 - 875
(2007/10/02)
-
- Stereoselective Synthesis of Alcohols containing (Z)- and (E)-Olefins, Dienes, Enynes and Styrenes: Cyclic β-Halogeno Scissions using Samarium Diiodide as the Electron-transfer Agent
-
In contrast to the sodium-mediated ring scission of 2-substituted 3-chloro ethers of the tetrahydrofuran series, samarium diiodide gives olefins of high (E)-stereoselectivity and provides (E)-conjugated and unconjugated dienes, styrenes and enynes in good yield without appreciable over-reduction.Whilst the SmI2 scission of 3-chloro-2-alkyltetrahydropyrans gives (Z)-rich (Z)/(E) olefin mixtures, the 2-(alk-1'-ynyl) members give (Z)-enyne alkohols with high stereoselectivity, providing a valuable complement to the (E)-enyne synthesis employing the tetrahydrofuran series.In electron-transfer scissions using sodium, the stereochemistry of the product alcohols is related to the ground-state conformation of the cis- and trans-pyrans and -furans.The slow SmI2-mediated reactions appear to involve samarium-complexed intermediates having structures independent of the original conformation, or of the cis- or trans-geometry of the furan or pyran, and it is the transition states from these intermediates that determine the stereochemical outcome.Scissions in the tetrahydrofuran series can be accelerated by addition of HMPA or DMPU with only a little deterioration in stereoselectivity, but in the tetrahydropyran series there are drastic changes in product stereochemistry when DMPU is added.Brief comment is made on the synthesis of tetrahydro-furan and pyran precursors.
- Crombie, Leslie,Rainbow, Linda J.
-
p. 673 - 688
(2007/10/02)
-
- Preparation of E-alkenes using lithium and 1,3-diaminopropane
-
A new selective reducing system, lithium in 1,3-diaminopropane, is described, which enables the preparation of E-olefins from acetylenes in high purity.
- Kovarova,Streinz
-
p. 2397 - 2404
(2007/10/02)
-
- Syntheses of cerulenin and its analogs. I. Cerulenin and its analogs with modified side chain
-
Optically active cerulenin 1, a potent inhibitor of fatty acid synthetase, was prepared via the condensation of the epoxy aldehyde 8 and the alkenyl lithium 16. In order to evaluate the effects of (E,E)-1,4-double bonds of the cerulenin side chain on the interaction with the enzyme, a series of optically active cerulenin analogs 32a-i with modified side chains and tetrahydrocerulenin 3 were synthesized by similar procedures.
- Morisaki,Funabashi,Furukawa,Shimazawa,Kanematsu,Ando,Okuda,Iwasaki
-
p. 2945 - 2953
(2007/10/02)
-
- Ring Scission Of Cyclic β-Halogeno-ethers with Samarium Di-iodide: A Synthesis of (E)- and (Z)-Enynols
-
The use of samarium di-iodide in place of sodium metal for the ring scission of cyclic β-halogeno-ethers drastically alters the stereochemistry of the resulting olefinic alcohols: using the method, highly stereoselective syntheses of enynols in (Z)- and (E)-forms are reported.
- Crombie, Leslie,Rainbow, Linda J.
-
p. 6517 - 6520
(2007/10/02)
-
- ACYL TRANSFER REACTIONS WITH PHOSPHINE OXIDES: SYNTHESIS OF E-HOMOALLYLIC ALCOHOLS, CYCLOPROPYL KETONES, AND γ-HYDROXY KETONES
-
Esters of 3-hydroxypropylphosphine oxides rearrange in base by O to C acyl (RCO) transfer to give the hydroxy ketones (8). threo-Selective reduction of (8) leads to pure E-homoallylic alcohols whilst C to O acyl )Ph2PO) transfer leads to γ-hydroxy ketones with nucleophilic aqueous base or cyclopropyl ketones with BuOKt - HOBut.
- Wallace, Paul,Warren, Stuart
-
p. 2971 - 2978
(2007/10/02)
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- One-Pot Synthesis of Substituted Homoallylic Alcohols (3-Alkenols) and 1,1-Dideuterio-3-alkenols
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The reaction of the lithium enolate of ethyl acetate with various α-chlorocarbonyl compounds followed by in situ reduction with lithium aluminium hydride or deuteride and then lithiation with lithium powder leads, after hydrolysis, to homoallylic alcohols in a regioselective manner.
- Barluenga, Jose,Alvarez, Flora,Concellon, Jose M.,Yus, Miguel
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p. 654 - 655
(2007/10/02)
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- Semiconductor Photocatalysis. Cis-Trans Photoisomerization of Simple Alkenes Induced by Trapped Holes at Surface States
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The use of ZnS or CdS as photocatalysts induces an efficient cis-trans photoisomerization of simple alkenes, e.g., the 2-octenes, 3-hexen-1-ols, and methyl 9-octadecenoates in photostationary cis-trans ratios almost identical with the thermodynamic equilibrium ratios achieved by the phenylthio radical.Quantum yields for the cis-trans photoisomerization, Φc-t, exceed largely over unity.Mechanistic studies involving Stern-Volmer analyses, quenching effect of oxygen, and ESR analysis under band-gap irradiation on ZnS in methanol demonstrate that the photoisomerizations take place with high turnover numbers at active sites where trapped holes at surface states, i.e., sulfur radicals arising from Zn vacancies and/or interstitial sulfur on sulfide semiconductors, play decesive roles.A highly efficient catalysis occurs with ZnS sols prepared from polysulfide-containing Na2S solution.The trapped-hole mechanism is further supported by the enhanced effect of water acting as a good electron acceptor as well as the quenching effect of diethylamine acting as an electron donor.
- Yanagida, Shozo,Mizumoto, Kunihiko,Pac, Chyongjin
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p. 647 - 654
(2007/10/02)
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- Vakuum UV Photolyses of Some Bichromophoric Alkenes Possesing Hydroxyl or Methoxycarbonyl Group
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The direct photolyses at 185 nm of some naturally occuring and related bichromophoric alkenes possesing hydroxyl or methoxycarbonyl group at an allylic, homoallylic, or remote position gave the geometrical isomers as the major photoproducts detectable on gas chromatography.The isomerization yield was highly sensitive to the functional group introduced and its position; allylic alkenols gave poor yields, while both functionalization at a remote position and esterification of the hydroxyl group improve the photoisomerization yield.
- Inoue, Yoshihisa,Goan, Kazuyoshi,Hakushi, Tadao
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p. 2217 - 2220
(2007/10/02)
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- β-Halogeno Ether Synthesis of Olefinic Alcohols: Stereochemistry of the Ring-scission of 2-Substituted 3-Halogenotetrahydro-pyrans and -furans
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The stereochemical outcome of the sodium ring-scission of 2-substituted 3-halogenotetrahydro-pyrans and -furans, with 2-substitution represented by alkyl, alkenyl or aryl, is presented.Although the cis- and the trans-tetrahydropyran scissions are hyghly stereoselective for (E)-5-substituted pent-4-enol, this stereoselectivity breaks down when the 2-substituent is conformationally undiscriminating (deuterium) or has substantial anomeric effects (methoxy).Consideration of this, along with conformational data from the preceding paper, provides an explanation of the stereoselectivity of the tetrahydropyran scission.Evidence against a radical, and for a carbanion intermediate is presented and a common, very rapidly inverting, 3-carbanion is considered to be formed from either cis- or trans-stereoisomers.Ring scission is also rapid (the carbanion cannot be trapped), but less rapid than carbanion inversion, and takes place before the slower conformational inversion can occur so that the (E)/(Z)-nature of the unsaturated alcohol produced is controlled by the initial tetrahydropyran conformation.The unstereospecific nature of the ring scission of both cis- and trans-2-alkyl-3-chlorotetrahydrofurans is explained as a consequence of their existence in conformational equilibria. The high stereoselectivity of the ring scission of cis- and trans-3-chloro-2,3-dimethyltetrahydropyrans, and the poor stereoselectivity of the scission of 2-alkyl-3-chloro-2-methyltetrahydrpyrans, is explained; the reaction of sodium with 2-butyl-3,3-dichlorotetrahydropyran is considered.Using the ring-scission of 3-chlor-2-ethyltetrahydropyran, short syntheses of (+/-)-endo-brevicomin are described to illustrate the utility of β-halogen ether synthesis.
- Crombie, Leslie,Wyvill, Robert D.
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p. 1983 - 1996
(2007/10/02)
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- Transition-Metal-Promoted Alkylations of Unsaturated Alcohols: The Ethylation of 3-Butyn-1-ol and 3-Buten-1-ol via Titanium Tetrachloride-Organoaluminum Ziegler-Natta Catalyst Systems
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Reaction of 3-butyn-1-ol with diethylaluminum chloride followed by treatment with titanium tetrachloride under a variety of conditions gave selectively up to 70 percent yields of (E)-3-hexen-1-ol, the product expected from a syn ethylmetalation of the multiple bond.No complications arising from in situ β-hydride elimination were observed.Similarly, 4-pentyn-2-ol was ethylated to give (E)-4-hepten-1-ol; however, 3-pentyn-1-ol did not give an ethylated product.Additionally, the effect of "third components", i.e., Lewis bases, on the ethylation of 3-butyn-1-ol and 3-buten-1-ol was studied.
- Schultz, F. W.,Ferguson, G. S.,Thompson, D. W.
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p. 1736 - 1739
(2007/10/02)
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- Novel Synthesis of (Z)-3-Hexen-1-ol and cis-Jasmone
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Both (Z)-3-hexen-1-ol and cis-jasmone were synthesised via 1,4-selective hydrogenation of conjugated dienes in the presence of arene Cr(CO)3 or Cr(CO)6 catalysts as the key step.
- Furuhata, Akimichi,Onishi, Ken,Fujita, Akira,Kogami, Kunio
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p. 1757 - 1760
(2007/10/02)
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- A CONVENIENT METHOD FOR THE STEREOSPECIFIC SYNTHESIS OF (E)-3-ALKEN-1-OLS UTILIZING THE RING-OPENING REACTION OF 2,3-DIHYDROFURAN WITH ORGANOCUPRATES
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(E)-3-Alken-1-ols were stereospecifically synthesized in good yields utilizing the regioselective nucleophilic ring-opening reaction of 2,3-dihydrofuran with several kinds of organocuprates under mild conditions.
- Fujisawa, Tamotsu,Kurita, Yoshitsugu,Kawashima, Masatoshi,Sato, Toshio
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p. 1641 - 1642
(2007/10/02)
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- Diaklylaluminum chloride catalyzed ene reactions of aldehydes. Synthesis of ipsenol
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Dimethylaluminum chloride which is a mild Lewis acid and a proton scavenger, catalyzes the ene reactions of aliphatic and aromatic aldehydes. Proton initiated rearrangements do not occur, since the alcohol-Lewis acid complex formed in the ene reaction rapidly to give methane and a non-acidic aluminum alkoxide.
- Snider, Barry B.,Rodini, David J.
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p. 1815 - 1818
(2007/10/02)
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