- Electrochemically driven desaturation of carbonyl compounds
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Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
- Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
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- Synthesis of aldehydes by a one-carbon homologation of ketones and aldehydes via --α,β-unsaturated isocyanides
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Ketones and aldehydes react via a Wittig-Horner-Emmons reaction using diethyl(isocyanomethyl)phosphonate to form α,β-unsaturated isocyanides (4), which are either hydrolyzed as such, under acid conditions, or hydrolyzed after oxidation to α,β-unsaturated isocyanates (6) to give aldehydes containing one additional carbon atom.The scope of the reaction is demonstrated by 20 examples.
- Moskal, Janusz,Leusen, Albert M. van
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- 2-(N'-alkylidenehydrazino)adenosines: Potent and selective coronary vasodilators
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The reaction of aliphatic aldehydes and ketones with 2-hydrazinoadenosine under relatively mild conditions (at room temperature or in refluxing methanol) formed 2-(N'-alkylidenehydrazino)-adenosines, 5-22, in good yields. Two kinds of adenosine receptors regulate cardiac and coronary physiology. In supraventricular tissues an A1AR coupled to muscarinic K channels mediates the negative chronotropic, dromotropic, and inotropic actions of adenosine, and an inhibitory A1AR coupled to adenylate cyclase mediates the 'antiadrenergic' action of adenosine. One or more kinds of A2 receptors mediate coronary vasodilation. Bioassays employing a guinea pig heart Langendorff preparation showed that 5-22 weakly retard impulse conduction through the AV node (negative dromotropic effect), but several analogues were very active coronary vasodilators. The coronary vasoactivity of the (n- alkylidene- and of the (isoalkylidenehydrazino)adenosines paralleled the length of the alkyl chain, the EC50s of the most active n-pentylidene (8) and isopentylidene (18) congeners being 1 nM. The EC50s of the cyclohexylmethylene (9), cyclohexylethylidene (10), and cyclohex-3- enylmethylene (12), analogues were likewise 50s of the negative dromotropic effects of 8, 9, and 18 by 5-28-fold and the EC50s of coronary vasodilation of 22-90-fold. Catalytic reduction of 9 increased the hydrophobicity and changed the UV spectrum, suggesting reduction of the -CH=N- bond. The product darkened on exposure to air and so was not characterized further. A new method for preparing 2',3',5'-tri-O- acetyl-2,6-dichloropurine riboside, a precursor in the synthesis of 2- hydrazinoadenosine, consists of the addition of tert-butyl nitrite to a mixture of 2',3',5'-tri-O-acetyl-6-chloroguanosine and CuCl in CHCl3 saturated with Cl2.
- Niiya,Olsson,Thompson,Silvia,Ueeda
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- Structure-activity relationships of xanthene carboxamides, novel CCR1 receptor antagonists
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The structure-activity relationships of xanthene carboxamide derivatives on the CCR1 receptor binding affinity and the functional antagonist activity were described. Previously, we reported a quaternarized xanthen-9-carboxamide 1 as a potent human CCR1 receptor antagonist that was derived from a xanthen-9-carboxamide lead 2a. Further derivatization of 2a focusing on installing an additional substituent into the xanthene ring resulted in the identification of 2b-1 with IC50 values of 1.8 nM and 13 nM in the binding assay using human CCR1 receptors transfected CHO cells and in the functional assay using U937 cells expressing human CCR1 receptors, respectively.
- Naya, Akira,Ishikawa, Makoto,Matsuda, Kenji,Ohwaki, Kenji,Saeki, Toshihiko,Noguchi, Kazuhito,Ohtake, Norikazu
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- Pd-Catalyzed Carbonylation of Vinyl Triflates to Afford α,β-Unsaturated Aldehydes, Esters, and Amides under Mild Conditions
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An efficient and general protocol for the synthesis of α,β-unsaturated aldehydes, esters, and amides via carbonylation of vinyl triflates including derivatives of camphor, ketoisophorone, verbenone, and pulegone was developed. Crucial for these transformations is the use of a specific palladium catalyst containing a pyridyl-substituted dtbpx-type ligand. This procedure also allows for an easy access of dicarbonylated products from the corresponding ketones.
- Zhang, Shaoke,Neumann, Helfried,Beller, Matthias
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p. 3528 - 3532
(2019/05/24)
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- Ring Expansion, Ring Contraction, and Annulation Reactions of Allylic Phosphonates under Oxidative Cleavage Conditions
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Oxidative cleavage of cycloalkenylalkylphosphonates 1 followed by treatment with base gives rise to homologated cycloalkenones 2 in good to excellent yields. Subjecting cycloalk-2-enylphosphonates 3 to identical conditions provides the one-carbon ring-contracted compounds 4 in excellent yields. Oxidative cleavage of γ,δ-unsaturated ketophosphonates 6 followed by treatment with base affords 2-cyclopenten-1-ones 7 in good overall yields. This method may offer a practical alternative to existing methods for effecting one-carbon ring expansion, ring contraction, and annulation reactions.
- Orr, Dupre,Yousefi, Nikolas,Minehan, Thomas G.
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p. 2839 - 2843
(2018/05/29)
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- Dehydrogenative Synthesis of Linear α,β-Unsaturated Aldehydes with Oxygen at Room Temperature Enabled by tBuONO
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Synthesis of linear α,β-unsaturated aldehydes via a room-temperature oxidative dehydrogenation has been realized by the cocatalysis of an organic nitrite and palladium with molecular oxygen as the sole clean oxidant. Linear α,β-unsaturated aldehydes could be efficiently prepared under aerobic catalytic conditions directly from the corresponding saturated linear aldehydes. Besides linear products, the aromatic analogy could also be smoothly achieved by the same standard method. The organic nitrite redox cocatalyst and alcohol solvent play a key role for realizing this method.
- Wang, Mei-Mei,Ning, Xiao-Shan,Qu, Jian-Ping,Kang, Yan-Biao
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p. 4000 - 4003
(2017/06/19)
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- Efficient Access to All-Carbon Quaternary and Tertiary α-Functionalized Homoallyl-type Aldehydes from Ketones
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β,γ-Unsaturated aldehydes with all-carbon quaternary or tertiary α-centers were rapidly assembled from ketones through a unique synthetic operation consisting of 1) C1 homologation, 2) Lewis acid mediated epoxide–aldehyde isomerization, and 3) electrophilic trapping. The synthetic equivalence of a vinyl oxirane and a β,γ-unsaturated aldehyde is the key concept of this previously undisclosed tactic. Mechanistic studies and labeling experiments suggest that an aldehyde enolate is a crucial intermediate. The homologating carbenoid formation plays a critical role in determining the chemoselectivity.
- Pace, Vittorio,Castoldi, Laura,Mazzeo, Eugenia,Rui, Marta,Langer, Thierry,Holzer, Wolfgang
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supporting information
p. 12677 - 12682
(2017/09/08)
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- COMPOUNDS AND METHODS OF TREATING OCULAR DISORDERS
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A method of treating an ocular disorder in a subject associated with increased all-trans-retinal in an ocular tissue includes administering to the subject a therapeutically effective amount of a primary amine compound of formula (I); and pharmaceutically acceptable salts thereof.
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- Two-Component Assembly of Thiochroman-4-ones and Tetrahydrothiopyran-4-ones Using a Rhodium-Catalyzed Alkyne Hydroacylation/Thio-Conjugate-Addition Sequence
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β′-Thio-substituted-enones, assembled from the combination of β-tert-butylthio-substituted aldehydes and alkynes, using rhodium catalysis, are shown to smoothly undergo in situ intramolecular S-conjugate addition to deliver a range of S-heterocycles in a one-pot process. Aryl, alkenyl, and alkyl aldehydes can all be employed, to provide thiochroman-4-ones, hexahydro-4H-thiochromen-4-ones, and tetrahydrothiopyran-4-ones, respectively. A variety of in situ oxidations are also performed, allowing access to S,S-dioxide derivatives, as well as unsaturated variants.
- Bouisseau, Ana?s,Glancy, John,Willis, Michael C.
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supporting information
p. 5676 - 5679
(2016/11/17)
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- Fe3O4 magnetic nanoparticles (MNPs) as an efficient catalyst for selective oxidation of benzylic and allylic C-H bonds to carbonyl compounds with tert-butyl hydroperoxide
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Fe3O4 magnetic nanoparticles (MNPs) were prepared by a co-precipitation method with oleic acid as a surfactant and characterized by FT-IR, TEM, DLS, XRD, VSM techniques. XRD, DLS and TEM analysis of this catalyst clearly showed the formation of cubic structure Fe3O4 MNPs, with a mean size of 16 nm. Moreover, a magnetization measurement revealed that the Fe3O4 MNPs had superparamagnetic behaviour and the saturation magnetization of the catalyst was 54.6 emu g-1. The Fe3O4 MNPs in combination with tert-butyl hydroperoxide catalyzed the oxidation of various benzylic and allylic C-H bonds to the corresponding carbonyl compounds in excellent yields. These oxidation reactions were effectively and economically performed under mild conditions, and therefore the dual challenge of cost effectiveness and benign nature of the processes was met.
- Zarghani, Monireh,Akhlaghinia, Batool
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p. 38592 - 38601
(2016/05/24)
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- Expansion of first-in-class drug candidates that sequester toxic all-trans-retinal and prevent light-induced retinal degeneration
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All-trans-retinal, a retinoid metabolite naturally produced upon photoreceptor light activation, is cytotoxic when present at elevated levels in the retina. To lower its toxicity, two experimentally validated methods have been developed involving inhibition of the retinoid cycle and sequestration of excess of all-trans-retinal by drugs containing a primary amine group. We identified the first-in-class drug candidates that transiently sequester this metabolite or slow down its production by inhibiting regeneration of the visual chromophore, 11-cis-retinal. Two enzymes are critical for retinoid recycling in the eye. Lecithin:retinol acyltransferase (LRAT) is the enzyme that traps vitamin A (all-trans-retinol) from the circulation and photoreceptor cells to produce the esterified substrate for retinoid isomerase (RPE65), which converts all-trans-retinyl ester into 11-cis-retinol. Here we investigated retinylamine and its derivatives to assess their inhibitor/substrate specificities for RPE65 and LRAT, mechanisms of action, potency, retention in the eye, and protection against acute light-induced retinal degeneration in mice. We correlated levels of visual cycle inhibition with retinal protective effects and outlined chemical boundaries for LRAT substrates and RPE65 inhibitors to obtain critical insights into therapeutic properties needed for retinal preservation.
- Zhang, Jianye,Dong, Zhiqian,Mundla, Sreenivasa Reddy,Hu, X. Eric,Seibel, William,Papoian, Ruben,Palczewski, Krzysztof,Golczak, Marcin
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p. 477 - 491
(2015/01/30)
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- Zn(II)- or Ag(I)-catalyzed 1,4-metathesis reactions between 3-en-1-ynamides and nitrosoarenes
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Catalyst-dependent metathesis reactions between 3-en-1-ynamides and nitrosoarenes are described. Particularly notable are the unprecedented 1,4-metathesis reactions catalyzed by Ag(I) or Zn(II) to give 2-propynimidamides and benzaldehyde derivatives. With 3-en-1-ynamides bearing a cycloalkenyl group, 1,4-oxoimination products were produced efficiently. We have developed metathesis/alkynation cascades for unsubstituted 2-propynimidamides and benzaldehyde species generated in situ, to manifest 1,4-hydroxyimination reactions of 3-en-1-ynes. Both 1,4-oxoiminations and 1,4-hydroxyiminations increase the molecular complexity of products.
- Gawade, Sagar Ashok,Huple, Deepak B.,Liu, Rai-Shung
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p. 2978 - 2981
(2014/03/21)
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- Neutral nazarov-type cyclization catalyzed by palladium(0)
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Joining the circle: The first Pd0 catalyzed Nazarov-type cyclization of diketoesters (see scheme) proceeds in 70 % to 95 % yield under strictly neutral pH conditions. Aryl substitution of the diketoesters is not required, so the reaction shows great versatility and can also proceed with aliphatic substrates. Copyright
- Shimada, Naoyuki,Stewart, Craig,Bow, William F.,Jolit, Anais,Wong, Kahoano,Zhou, Zhe,Tius, Marcus A.
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supporting information; experimental part
p. 5727 - 5729
(2012/08/07)
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- Synthesis and comparative antibacterial activity of verdamicin C2 and C2a. A new oxidation of primary allylic azides in dihydro[2H]pyrans
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(Chemical Equation Presented) A synthesis of verdamicin C2 and its congener C2a has been accomplished from sisomicin relying on a novel oxidative transformation of an allylic azide to the corresponding α,β- unsaturated aldehyde, and its stereocontrolled elaboration into the intended 5′ side chain of verdamicin C2 and C2a. In vitro antibacterial testing shows that both C6′ epimers in verdamicin C2 and C2a are equally active against a variety of bacterial strains. Oxidation of allylic primary azides, ethers, and esters of 2-substituted dihydro[2H]pyrans with SeO2 leads directly to the corresponding aldehydes.
- Hanessian, Stephen,Szychowski, Janek,Pablo Maianti
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supporting information; experimental part
p. 429 - 432
(2009/09/25)
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- Selective oxidation of aromatic primary alcohols to aldehydes using molybdenum acetylide oxo-peroxo complex as catalyst
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Selective oxidation of various aromatic alcohols to aldehydes has been carried out with very high conversion (90%) and selectivity (90%) for aldehydes using cyclopentadienyl molybdenum acetylide complex, CpMo(CO)3(C{triple bond, long}CPh) (1) as catalyst and hydrogen peroxide as environmentally benign oxidant. Water-soluble Mo acetylide oxo-peroxo species is formed in situ after reaction of 1 with aqueous hydrogen peroxide during the course of reaction as catalytically active species. Interestingly even though the catalyst is homogeneous it could be recycled very easily by separating the products in organic phase and catalyst in aqueous phase using separating funnel. Even after five recycles no appreciable loss in alcohol conversion and aldehyde selectivity was observed.
- Biradar, Ankush V.,Dongare, Mohan K.,Umbarkar, Shubhangi B.
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experimental part
p. 2885 - 2888
(2009/09/06)
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- Palladium catalysts for the formylation of vinyl triflates to form α,β-unsaturated aldehydes
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(Chemical Equation Presented) What a gas! Synthesis gas is the formylating agent in the efficient one-step title transformation promoted by a palladium catalyst with the bidentate ligand 1,2-bis(di-1-adamantylphosphinomethyl)benzene (see scheme). This method enables the conversion of six-to eight-membered-ring triflates into α,β-unsaturated aldehydes and the introduction of a formyl group into derivatives of elaborate natural compounds. Tf = trifluoromethanesulfonyl.
- Neumann, Helfried,Sergeev, Alexey,Beller, Matthias
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scheme or table
p. 4887 - 4891
(2009/02/08)
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- Anomalous intramolecular C-H insertion reactions of rhodium carbenoids: Factors influencing the reaction course and mechanistic implications
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The intramolecular insertion of rhodium carbenoids into the α-C-H bonds of allylic ethers to give 3(2H)-furanones has been explored. Cyclopropanation is favored irrespective of the complex used for carbenoid generation or the substitution pattern of the allylic ether, unless a substituent is placed on the tether connecting the ether to the α-diazo ketone. Unusual acetal products resulting from an anomalous C-H insertion process are obtained in addition to the expected 3(2H)-furanones formed by conventional carbenoid C-H insertion. These acetals are the favored C-H insertion products in certain circumstances and particularly in cases where carbenoid generation is effected using an electron-deficient rhodium complex. Experiments with simple deuterium labeled substrates reveal that anomalous C-H insertion products arise by a mechanism that is distinct from that leading to the formation of conventional C-H insertion products. The formation of acetal products and the outcome of reactions performed using deuterium-labeled substrates suggest that a mechanism involving hydride migration to the rhodium center of the carbenoid is operative.
- Clark, J. Stephen,Dossetter, Alexander G.,Wong, Yung-Sing,Townsend, Robert J.,Whittingham, William G.,Russell, C. Adam
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p. 3886 - 3898
(2007/10/03)
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- A convenient route to α,β-unsaturated aldehydes based on polymer-supported α-selenoaldehydes
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Polystyrene-supported (4-phenylseleno)morpholine was synthesised and could be used as an efficient α-selenenylating agent for saturated aldehydes; subsequent oxidation of polystyrene-supported α-selenoaldehydes and the products from the Wittig reaction of them with chloromethylidenetriphenylphosphorane with an excess of 30% hydrogen peroxide at room temperature afforded α,β-unsaturated aldehydes in good yields and purities.
- Sheng, Shou-Ri,Wu, Lu-Ling,Huang, Xian
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p. 258 - 259
(2007/10/03)
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- Synthesis and application of novel catalytically active polymers containing 1,4,7-triazacyclononanes
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New polymers containing 1,4,7-triazacyclononanes have been synthesised by means of ring opening metathesis polymerisation (ROMP); their complexes with Mn(II) catalyse the oxidation of simple olefins by hydrogen peroxide.
- Grenz,Ceccarelli,Bolm
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p. 1726 - 1727
(2007/10/03)
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- Lewis-acid-promoted reactions of 1(tributylstannyl)methoxy>cyclohexene
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As a model for a synthetic approach to taxol and taxotere, the condensation of recemic α-alkoxy allylic stannane 9 with aldehydes 10a-h was examined.Under BF3*OEt2-promoted reactions, the syn-E 11a-h homoallylic alcohols were obtained as the major isomers.EtAlCl2 was found to be an efficient promoter for the condensation of aldehyde 10e,f.With β or α-hydroxyaldehydes 10g or 10h in the presence of intramolecular chelated MgBr2, the stereochemical outcome of the reaction was inverted to give, in high yield and good stereoselectivity, the anti-E 11g,h homoaldol products exhibiting the stereochemistry required for the synthesis of taxanes. - Keywords: α-alkoxyallylic stannane; homoaldol reaction; homoallylic alcohol; Lewis-acid-promoted reaction; taxol; taxotere
- Muller, Benoit,Ferezou, Jean-Pierre,Pancrazi, Ange,Lallemand, Jean-Yves
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- Synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters
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The synthesis of (R)- and (S)-2-hydroxy-3-enoic acid esters [(R)-1a-d and (S)-1a-c] is described. The (R) enantiomers were prepared by a Pinner synthesis from the corresponding (R)-cyanohydrins [(R)-2a-d], which in turn were obtained by R-oxynitrilase- (E.C. 4.1.2.10)-catalyzed addition of HCN to the α,β-unsaturated aldehydes 3a-d. For the preparation of the (5) enantiomers an inversion of the configuration had to be implemented. A critical evaluation of the two possible sequences: inversion of the configuration of the cyanohydrins followed by solvolysis of the nitrile function, and solvolysis of the cyanohydrins followed by inversion of the configuration of the resulting α-hydroxy esters, came out in favor of the latter pathway.
- Warmerdam,Van Den Nieuwendijk,Kruse,Brussee,Van Der Gen
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- Palladium catalysed conversion of vinyl bromo allylic alcohols into vinylic carbonyl compounds and oxidation of secondary alcohols to ketones
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A variety of vinyl bromo allylic alcohols are converted into the corresponding vinylic carbonyl compounds and secondary alcohols are oxidised into ketones upon treatment with palladium acetate in the presence of potassium carbonate under the typical Heck reaction conditions.
- Pitre, Sangceta V.,Vankar, Padma S.,Vankar, Yashwant D.
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p. 12291 - 12298
(2007/10/03)
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- Synthesis of aromatic and αβ-unsaturated aldehydes by a friedel-crafts-like electrophilic destamylation using 1,1-dichloromethyl metyhyl ether
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A mild and effective method for the preparation of a variety of aromatic (7a-m), heteroaromatic (7n-r), and α,β-unsaturated aldehydes (8a-f) is described. The reaction of trialkylaryl- (2a-o), heteroaryl- (2p-t), and 1-alkenylstannanes (4a-f and 5a-f) with dichloromethyl methyl ether (1, DCME) in the presence of aluminium trichloride followed by hydrolysis provides the corresponding aldehydes. In the case of arylstannanes the ipso-isomers are generally formed; the p-alde-hydes occur as side products. The electrophilic substitution of 1-alkenylstannanes with 1 leads to α,β-unsaturated aldehydes In an ipso- and stereospecific manner. A comparison of the leaving abilities of the stannyl and silyl groups shows a lower or even zero reactivity of the silyl-substituted compounds 8a-e towards the electrophile 1. In the silylstannylalkene 6c only the stannyl group reacts whereas the stannyl function remains unaffected in the product, aldehyde 11.
- Niestroj, Michael,Neumann, Wilhelm P.
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- Facile One Pot Thermal Dehydration and Dethioacetalization of β-Hydroxydithioacetals with Dimethyl sulphoxide: Synthesis of α,β-Unsaturated Aldehydes
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The acyclic and cyclic β-hydroxydithioacetals 3a-m and 4a-b obtained by sodium borohydride reduction (or Grignard addition) of the corresponding β-oxodithioacetals 2a-m are shown to undergo facile one pot thermal dehydration and dethioacetalization in the presence of dimethyl sulphoxide to afford the corresponding ene- and polyene aldehydes 5a-m and 6a-b in good yields.The probable mechanism of dethioacetalization with dimethyl sulphoxide has also been discussed.
- Rao, Ch. Srinivasa,Chandrasekharam, M.,Patro, Balaram,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
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p. 5783 - 5794
(2007/10/02)
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- Rhodium complex catalyzed hydroformylation reactions of linear and cyclic mono- and diolefins
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The hydroformylation reactions of cyclopentene, cyclohexene, 4-vinylcyclohexene, cycloheptene and cyclooctene, catalyzed with a Rh(acac)2/P(OPh)3 (I) system at 80 deg C and 10 atm (CO+H2), have been studied.Only cyclopentene and 4-vinylcyclohexene undergo hydroformylation at 1 atm and 40 deg C.The hydroformylation of some cyclic dienes; (1,3- and 1,4-cyclohexadienes, 1,3- and 1,5-cyclooctadienes and 1,3-cyclopentadiene), at 10 atm and 80 deg C, was investigated in two catalytic systems: (I) and Rh(acac) (CO) (PPh3) / PPh3 (II).The main reaction products of cyclohexadienes and pentadiene (at 80 deg C, 10 atm) are unsaturated monoaldehydes.In hydroformylation of 1,5-cyclooctadiene the main product is formylcyclooctane.Key words: Rhodium; Olefins; Hydroformylation
- Trzeciak, Anna M.,Ziolkowski, Jozef J.
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p. 213 - 216
(2007/10/02)
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- Electrophilic Additions to the Bicyclobutane System of Tricyclo2,7>heptane Derivatives: Halogen Electrophiles
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The known reactions of 8,8-dibromotetracyclo2,4.03,5>octane (3a) and homobenzvalene (7) with pyridinium bromide perbromide and iodine, respectively, were carried out in the presence of tetra-n-butylammonium chloride.The formation of the chloro-substituted norpinane derivatives 6a and 9 is evidence for cationic intermediates.The same mechanism is operative in the reaction of pyridinium bromide perbromide with the dichlorotetracyclooctane 3b, which was prepared from 7 and dichlorocarbene.On exposure of tricyclo2,7>heptane (1) to N-bromosuccinimide in acetone/water/triethylamine, the bromonorpinanol 22, the bromonorcaranols 23, and cyclohex-1-ene-1-carboxaldehyde (24) were obtained.On the basis of the steric course and thermodynamic considerations, the cationic intermediates generated in the above reactions by attack of the electrophiles at the bicyclobutane systems are assigned the halonium ion structure 38 and the nonclassical structures 34 and 35, respectively.Elemental bromine and iodine converted the phenyltricycloheptane 10 into the respective diastereomeric norpinanes 11 and 12, which were transformed smoothly into the diastereomeric methyl ethers 13 and 14 treatment with sodium methoxide in methanol.The reactions of 10 with pyridinum bromide perbromide in pyridine, cyanogen bromide in the presence of aluminium trichloride, and N-bromosuccinimide in acetone/water gave rise to norpinane derivatives, i.e. the pyridinium salt 15, the nitrile 16, and the alcohol 18, respectively.In the case of cyanogen iodide in acetonitrile, the solvent participated in the process to yield the 2-(norpinylimino)propionitriles 17.Corresponding to the configurations of the products, the attack of a halogen electrophile at 10 leads to classical 6-phenyl-6-norpinyl cations 41, which may be approached by nucleophiles from the two possible faces.As origin for the low tendency of the cations 33-35 and 41 to rearrange to norcaryl cations, the electronegativity of the halogen atoms is suggested.The reduced migratory aptitude of a CHHal relative to a CH2 group results from its electron deficiency and from the decreased stability of 7-halo-2-norcaryl relative to the parent 2-norcaryl cations.The chlorophenyltricycloheptane 25 was prepared from 10 and treated with aqueous sulfuric acid to give the norpinanol 27.Formed by protonation of the bicyclobutane system of 25, the cationic precursor of 27 shows a behaviour similar to that of cations 41. - Key Words: Norpinanes, preparation / Carbocations, classical and nonclassical / Neighbouring group participation / Halonium ions / Migratory aptitudes in carbocations
- Gerstner, Erwin,Kemmer, Ralf,Christl, Manfred
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p. 381 - 392
(2007/10/02)
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- Initiated tert-Butyl Hydroperoxide-loaded Low-temperature Autoxidation of Alkenes: Alternative Hydroperoxide Syntheses and the Preparation of a Complete Set of Reference Material
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A complete set of characterization data for the allylic hydroperoxides prepared from 1-methylcyclohexene and the isomeric 4-methyloct-4-enes is presented.The data relies upon the preparation of allylic hydroperoxides by tert-butyl hydroperoxide-loaded autoxidations, singlet-ene oxidations and nucleophilic substitution reactions.Appropriate allylic alcohols and relevant scission products have been prepared to support the assignments given.
- Courtneidge, John L.,Bush, Melanie,Loh, Lay-See
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p. 1539 - 1548
(2007/10/02)
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- AUXILIARY-DIRECTED DIOXYGENATION: STEREOSELECTIVE SYNTHESIS OF A DIENE HYDROPEROXIDE
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The presence of a chiral auxiliary is shown to induce highly stereoselective peroxidation of a tethered 1,4-diene.
- Dussault, Patrick H.,Hayden, Michael R.
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p. 443 - 446
(2007/10/02)
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- Reactions of unactivated olefins with Vilsmeier reagents
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Reactions of N-formylmorpholine/POCl3 with several unactivated olefins yield the corresponding α,β-unsaturated aldehydes.Norbornene affords with dimethylformamide/POCl3 a product formed by a novel inverse-electron demand Diels-Alder reaction of an acyclic 2-azoniodiene.The structure of this product was confirmed by X-ray analysis.Crystals are monoclinic: a = 8.025(3), b = 11.670(3), c = 9.309(4) Angstroem, β = 108.03(3) deg, P21,Z = 2; the structure was refined to R = 0.044 for 1379 independent observed reflections.
- Katritzky, Alan R.,Shcherbakova, Irina V.,Tack, Robert D.,Steel, Peter J.
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p. 2040 - 2045
(2007/10/02)
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- Synthesis with organoboranes V. Hydroxymethylation and formylation of cycloalkenes via allylic organopotassium and organoboron compounds
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Allylic hydroxymethylation of cyclohexene and cyclooctene was achieved by metallation with trimethylsilylmethylpotassium followed by the reaction with formaldehyde. 1-Methylcycloalkenes were transformed into 2-methylenecycloalkane-1-methanols by the reaction of formaldehyde with allylic diethylboranes derived from these olefins via metallation-transmetallation.Conjugated cycloalkenecarboxaldehydes were obtained by oxidation of the hydroxymethylation products.
- Zaidlewicz, Marek
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p. 103 - 107
(2007/10/02)
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- Selective Isomerization of Glycidates and Their Analogues with Triphenylsilyl Perchlorate or Electrogenerated Acid
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Isomerization of glycidic esters and nitriles to the corresponding 2-hydroxy-3-alkenoates and their nitrile derivatives occurred on treatment with triphenylsilyl perchlorate or electrogenerated acid (EG acid).The cyanohydrin moiety of the nitriles 4 was transformed to a formyl group, giving the corresponding enals on treatment with weak base.
- Inokuchi, Tsutomu,Kusumoto, Masahiko,Matsumoto, Sigeaki,Okada, Hiroyuki,Torii, Sigeru
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p. 2009 - 2012
(2007/10/02)
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- OXIDATION OF ALDEHYDES TO α,β-UNSATURATED ALDEHYDES VIA α-CHLOROALDIMINES
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The oxidation of aldehydes to α,β-unsaturated aldehydes has been performed by a sequence of reactions involving conversion into aldimines, chlorination at the α-position to form α-chloroaldimines, base-induced dehydrochlorination and hydrolysis.The four-step transformation can be executed without isolation of the intermediates.This method has been applied to the synthesis of an artificial flavor, i.e. 2-butyl-3-phenylpropenal.
- Kimpe, Norbert De,Stevens, Christian
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- A Simple Method for Producing Cycloalkenyllithiums from Cycloalkanones via Reductive Lithiation of Enol Phenyl Thioethers
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Cyclohexenyl, cycloheptenyl, and cyclooctenyl phenyl sulfides, readily prepared from the corresponding cycloalkanones, are reductively lithiated by lithium p,p'-di-tert-butylbiphenylide to produce cycloalkenyllithiums in good yields.
- Cohen, Theodore,Doubleday, Mary Dosch
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p. 4784 - 4786
(2007/10/02)
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- Barium Permanganate, Ba(MnO4)2, a versatile and mild oxidizing agent for use under aprotic and non-aqueous conditions
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Barium Permanganate is an easily prepared, stable, and a versatile oxidation reagent. With this reagent different types of primary and secondary hydroxy compounds are converted to their carbonyl derivatives. Aldehydes could be transformed to their carboxylic acids. Benzylic chloride and bromides are converted to their aldehydes and carboxylic acids. Semicarbazide and 2,4-dinitrophenylhydrazine derivatives of benzylic carbonyl compounds undergo carbon-nitrogen bond cleavage selectively and yield the expected carbonyl compounds. p-Hydroquinone is converted to p-benzoguinone and aromatic amines to their azo compounds. Anthracene and phenanthrene produce their 9,10-quinones. Diphenyl acetylene and trans stilbene give benzil, and styrene produces benzaldehyde. Selective oxidations of secondary benzylic carbon-hydrogen bonds occur and the corres- ponding carbonyl compounds are produced in good yields.
- Firouzabadi,Seddighi,Mottaghineiad,Bolourchian
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p. 6869 - 6878
(2007/10/02)
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- Isomerisation de dienes-1,5 fonctionnalises par le fer pentacarbonyle
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A series of various, functionnalized 4-vinylcyclohexene derivatives, substituted with electron-withdrawing or -donating groups on the exocyclic double bond, have been isomerized by pentacarbonyliron, under thermodynamic control with heating, into a mixture of conjugated cyclohexadiene tricarbonyliron complexes, of which the 2-substituted derivative is the predominant.When ferrous chloride is used as the co-catalyst, the isomerisation proceeds under kinetic control to give the 1-substituted cyclohexadienetricarbonyliron complex as the major derivative.Reaction mechanisms, have been proposed for these isomerisation processes, which provide a new selective route to such derivatives.The formation of η4-1,4-cyclohexadienetricarbonyl complexes as intermediates has been excluded, and it is shown that the thermal isomerisation proceeds via η2-complexes that are formed by successive 1,3-hydrogen shifts.
- Rodriguez, J.,Brun, P.,Waegell, B.
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p. 343 - 370
(2007/10/02)
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- Synthesis and Reaction of (3-Phenylseleno-1-alkenyl)triphenylphosphonium Salts
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The reaction of allylic triphenylphosphonium ylides with benzeneselenenyl bromide gave (3-phenylseleno-1-alkenyl)triphenylphosphonium salts in good yields.Oxidation of the salts produced α,β-unsaturated aldehydes.
- Minami, Toru,Nakayama, Minoru,Nakamura, Taku,Okada, Yoshiharu
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p. 1741 - 1742
(2007/10/02)
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- USE OF MOIST SILICA GEL FOR OBTAINING α-ETHYLENIC CARBONYL COMPOUNDS FROM Β-ALKYLTHIO OR β-PHENYLTHIO ALLYLIC ALCOHOLS.
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The β-alkylthio and β-phenylthio α-ethylenic aldehydes 2, (Z)-6, (E)-6 and 9 were obtained from the corresponding β-chloro α-ethylenic aldehydes, and the α-phenylthiometylidene ketones (Z)-13 and (E)-13 by Peterson reaction with α,α-dimethoxycyclohexanone followed by deacetalization.Reduction (NaBH4) or addition of organolithium compounds led to allylic alcohols which gave α-ethylenic carbonyl compounds with removal of thiol or thiophenol after treatment by moist acidic silica gel with or without mercuric chloride.The method also worked for oxygenated compounds 21, 22.
- Pellet, Michele,Huet, Francois
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p. 4463 - 4468
(2007/10/02)
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- Bacteriorhodopsin. The influence of the cyclohexene-ring methyls
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Four ring-demethylated retinals, viz. 1,1',5-tridemethylretinal, 1,1'-didemethylretinal, 1,5-didemethylretinal and 1-demethylretinal, have been synthesized via new and simple schemes.The properties of these modified retinals, their protonated Schiff bases and the corresponding bacteriorhodopsins have been studied and compared with the native system.These bacteriorhodopsin analogues have also been tested for their proton-pump efficiencies.A large decrease in proton-pump activity was found for the analogues lacking the 5-methyl group.On the whole, the opsin shifts of the modified bacteriorhodopsins were much lower than those of the native system.UV-Vis and 1H NMR data support a planar 6-s-trans conformation for the demethylated retinals in solution rather than a twisted 6-s-cis conformation (torsion angle 40-60 deg) as found in retinal.This explains the lower opsin shift and the better fit of these demethylated retinals in bacteriorhodopsin's binding site, which, in its native form, contains a 6-s-trans chromophore.
- Courtin, J. M. L.,Verhagen, L.,Biesheuvel, P. L.,Lugtenburg, J.,Bend, R. L. van der,Dam, K. van
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p. 112 - 119
(2007/10/02)
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- New Methods for the Syntheses of α,β-Unsaturated Ketones, Aldehydes, and Nitriles by the Palladium-Catalyzed Reactions of Allyl β-Oxo Esters, Allyl 1-Alkenyl Carbonates, and Allyl α-Cyano Esters
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Allyl β-oxo esters, allyl 1-alkenyl carbonates, and allyl α-cyano esters are converted into α,β-unsaturated ketones, aldehydes, and nitriles by palladium-catalyzed intramolecular decarboxylation-dehydrogenation.Palladium-phosphine complexes such as Pd(OAc)2-PPh3, Pd(OAc)2-dppe, or Pd2(dba)3*CHCl3-PPh3, are effective catalysts.Yields depend on solvents and on the mole ratio of palladium to phosphine.The optimum Pd/P ratio for each substrate was determined.Use of nitriles as solvents is essential for the dehydrogenation.
- Minami, Ichiro,Nisar, Mohammad,Yuhara, Masami,Shimizu, Isao,Tsuji, Jiro
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p. 992 - 998
(2007/10/02)
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- Syntheses of α-Iodocarbonyl Compounds Using Bis(sym-collidine)Iodine(I) Tetrafluoroborate/Dimethyl Sulfoxide
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I(1+)(Collidine)2BF4(1-)/DMSO has been found to be a convenient reagent for the direct conversion of alkenes to α-iodocarbonyl compounds.Using conformationally biased alkenes, the reactions proceed stetreospecifically giving axial iodoketones.Application of the reagent in reactions with unsaturated carbohydrates provides a unique method for the conversion of certain glycals to their corresponding α-iodo-α,β-unsaturated lactones.
- Evans, Robert D.,Schauble, J. Herman
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p. 727 - 730
(2007/10/02)
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- AZO ANIONS IN SYNTHESIS. PT 1. t-BUTYLHYDRAZONES AS ACYL-ANION EQUIVALENTS
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The lithium salts of aldehyde t-butylhydrazones react with electrophiles (aldehydes, ketones, alkyl halides, crotonates) to form C-trapped t-butylazo-compounds; tautomerisation and hydrolysis gave α-hydroxy ketones, ketones, and γ-keto esters in good yield, thereby providing a convenient new acyl-anion equivalent.Reaction of these lithium salts with aldehydes and ketones, followed by elimination provided a new route to azo alkenes.
- Baldwin, Jack E.,Adlington, Robert M.,Bottaro, Jeffrey C.,Kolhe, Jayant N.,Perry, Matthew W. D.,Jain, Ashok U.
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p. 4223 - 4234
(2007/10/02)
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- NEW SYNTHETIC METHODS FOR α,β-UNSATURATED KETONES, ALDEHYDES, ESTERS AND LACTONES BY THE PALLADIUM-CATALYZED REACTIONS OF SILYL ENOL ETHERS, KETENE SILYL ACETALS, AND ENOL ACETATES WITH ALLYL CARBONATES
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Silyl enol ethers and ketene silyl acetals derived from ketones, aldehydes, esters and lactones are converted into α,β-unsaturated ketones, aldehydes and lactones by treatment with allyl carbonates in high yields using the palladium-bis(diphenylphosphino)ethane (dppe) complex as catalyst.Phosphine-free palladium catalyst instead of the palladium-phosphine complex gives a higher selectivity for the preparation of cyclopentenone, cyclooctenone, dienones, α,β-unsaturated esters and lactones.As a solvent, the use of nitriles such as acetonitrile is essential.In other solvents, allylation takes place.Enol acetates derived from ketones are converted into α,β-unsaturated ketones by reaction with allyl carbonate in acetonitrile using the palladium complex and tributyltin methoxide as bimetallic catalysts.
- Minami, Ichiro,Takahashi, Kazuhiko,Shimizu, Isao,Kimura, Tsuneo,Tsuji, Jiro
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p. 2971 - 2978
(2007/10/02)
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- OXYDATION D'ALCENES CYCLIQUES PAR L'IODYLBENZENE CATALYSEE PAR L'ACETYLACETONATE DE VANADYLE
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Iodylbenzene with vanadyl acetylacetonate oxidizes cyclic alkenes, the experimental results accord with a free radical oxidation mechanism.
- Barret, R.,Pautet, F.,Daudon, M.,Mathian, B.
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p. 439 - 440
(2007/10/02)
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- Alcoxymethyltributyletains precurseurs d'alcoxymethyllithiums: application a la synthese de monoethers d'α-glycols et a l'homologation de cetones en aldehydes
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Ethoxymethyltributyltin (obtained from diethoxymethyltributyltin, acetyl chloride and tributyltin hydride) and methoxymethyltributyltin (obtained from chloromethyl-methyl ether and tributylstannylmagnesium chloride) have been transmetallated with butyllithium to give the corresponding alkoxymethyl lithium reagents.This reaction, although usually performed in ether, is possible in a variety of other solvents thus simplifying some of the problems encountered during isolation of the products.The alkoxymethyllithiums obtained react with aldehydes and ketones to give cleanly the corresponding monoprotected α-glycols.Stereochemical trends were observed for hydratropaldehyde and 4-tertiarybutylcyclohexanone, while regiochemical trends were evaluated in the case of cyclohexen-2-one.Syntheis of aldehydes has been achieved in good yields from tertiary monoprotected α-glycols using conventional methods.
- Duchene, Alain,Mouko-Mpegna, David,Quintard, Jean-Paul
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p. 787 - 793
(2007/10/02)
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- Synthesis of α,β-Unsaturated Aldehydes by 1,3-Carbonyl Transposition through One Carbon Homologation. Part 2
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The easily accessible 2-(diethoxymethyl)-6-methoxy-1-tetralone (1) on condensation with methylmagnesium iodide and benzylmagnesium chloride followed by treatment with BF3*Et2O affords 6-methoxy-1-methyl-3,4-dihydro-2-naphthaldehyde (2) and 1-benzyl-6-methoxy-3,4-dihydro-2-naphthaldehyde (3), respectively.The carbinols derived from the reaction of 2-(diethoxymethyl)-1-indanones (4a-4c) with methyllithium undergo smooth transformations to the respective 3-methyl-1H-indene-2-aldehydes (5a-5c). endo-2-(p-Methoxyphenyl)-5-methylbicyclooctan-6-en-7-aldehyde (14) has been prepared from endo-2-(p-methoxyphenyl)-5-methylbicyclooctan-6-one (12) through the respective diethoxymethyl derivative (12) by sodium borohydride reduction followed by acid-catalysed rearrangement of the resulting diacetal carbinol.
- Chakraborti, Ratna,Deb, Soumitra,Ghatak, Usha Ranjan
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p. 883 - 886
(2007/10/02)
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- A SIMPLE SYNTHESIS OF α,β-UNSATURATED ALDEHYDES BY 1,3-CARBONYL TRANSPOSITION THROUGH ONE CARBON HOMOLOGATION
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α,β-Unsaturated aldehydes are conveniently prepared from ketones through their β-diethoxymethyl derivatives by sodium borohydride reduction followed by acid-catalysed rearrangement of the resulting diacetal carbinols.
- Dasgupta, Ratna,Ghatak, Usha Ranjan
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p. 1581 - 1584
(2007/10/02)
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- Structure-Activity Relationship of the Warburgia Sesquiterpene Dialdehydes
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Sesquiterpene dialdehydes, isolated originally as insect antifeedants from East African Warburgia trees, have been shown to exhibit strong antimicrobial activity.Their chemical reactivities and biological activities were investigated in comparison with those of related compounds.There was a good correlation between the antifungal activity and the papain inhibitory activity of these compounds.Both activities appear to result from their highly specific reactivity with sulfhydryl groups.Consideration of the structure-activity relationships led to the proposal of a structure unit, the enal-aldehyde moiety, that is essential to biological activity.
- Taniguchi, Makoto,Adachi, Takeshi,Oi, Susumu,Kimura, Akihiko,Katsumura, Shigeo,et al.
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