- The α-arylation of α-bromo- and α-chloroenones using palladium-catalysed cross-coupling
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The palladium-catalysed cross-coupling reaction of various arylboronic acids with α-bromoenones and α-chloroenones offers an operationally simple approach to the synthesis of both cyclic and acyclic α-arylenones.
- Banks, James C.,Mele, David Van,Frost, Christopher G.
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Read Online
- Palladium-catalyzed trimerization of strained cycloalkynes: Synthesis of decacyclene
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Palladium-catalyzed cyclotrimerization was applied to three strained cycloalkynes. Pd(PPh3)4 and Pt(PPh3)4-catalyzed cyclotrimerizations of cyclohexyne (2) afforded dodecahydrotriphenylene (3) in 64% and 62% yields, respectively, but subjecting cyclopentyne to the same conditions failed to afford isolable amounts of the cyclotrimer. Finally, decacyclene (15), a putative C60-fullerene precursor, was obtained in 23% yield by Pd2(dba)3-catalyzed cyclotrimerization of acenaphthyne (14).
- Iglesias, Beatriz,Pe?a, Diego,Pérez, Dolores,Guitián, Enrique,Castedo, Luis
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- Diels-Alder routes to angularly halogenated cis-fused bicyclic ketones: Readily accessible cyclynone intermediates
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We have developed an efficient Lewis acid-catalyzed Diels-Alder route to a series of cis-fused bicyclic ketones bearing quaternary halogenation at the angular position. We have also developed a Diels-Alder-based one-flask method for the regioselective pre
- Lee, Jun Hee,Kim, Woo Han,Danishefsky, Samuel J.
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Read Online
- Enantioselective construction of the tricyclic core of curcusones A-D: Via a cross-electrophile coupling approach
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Herein we report our recent progress toward the enantioselective total synthesis of the diterpenoid natural products curcusones A-D by means of complementary Stetter annulation or ring-closing metathesis (RCM) disconnections. Using the latter approach, we
- Wright, Austin C.,Stoltz, Brian M.
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Read Online
- Photocycloaddition Chemistry of 2-(Trimethylsilyl)cyclopentenone and 5-(Trimethysilyl)uracil. The Utility of a Trimethylsilyl Group as a Removable Directing Group in Photochemistry
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The photocycloaddition reactions of 2-(trimethylsilyl)cyclopentenone with isobutylene, methylenecyclohexane, isopropenyl acetate, propylene, and propyne were investigated. In the first three cases, a regiospecific reaction giving the head-to-tail photoadd
- Shih, Chuan,Fritzen, Edward L.,Swenton, John S.
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- A remarkably simple one-step procedure for the preparation of α-bromo-α,β-unsaturated carbonyl compounds
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An easy and convenient one-step procedure for the conversion of α,β-unsaturated carbonyl compounds into their corresponding bromo-enones using NBS-Et3N·3HBr in the presence of potassium carbonate in dichloromethane at 0°C to room temperature under very mild conditions in high yields and significantly shorter times, is reported. Georg Thieme Verlag Stuttgart.
- Jyothi, Divya,Hariprasad
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Read Online
- Studies on DNA cleaving agents: Synthesis and chemically induced cycloaromatization of a monocyclic neocarzinostatin chromophore analogue
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The synthesis of an acyclic analogue of neocarzinostatin chromophore is described. This analogue is found to undergo cycloaromatization in the presence of thiols; the process involves a previously undetected internal hydrogen abstraction reaction.
- Wender, Paul A.,Tebbe, Mark J.
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Read Online
- Asymmetric conjugate addition to α-halo enones: Dramatic effect of styrene on the enantioselectivity
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A simple trick could prove generally valuable for asymmetric copper-catalyzed conjugate addition reactions. It was found that the enantioselectivities of such reactions of dialkyl zinc reagents with α-halo enones in the presence of chiral phosphorimidite
- Li, Kangying,Alexakis, Alexandre
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- A mild preparation of α-halo-α,β-enones from cyclic enones
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A simple one pot procedure flor the selective transformation of cyclic enones into α-halo-α,β-enones is reported using dimethyldioxirane and metal halides/Amberlyst 15. The method appears particularly appealing for the preparation of labelled molecules for use with the CMIA technique.
- Righi, Giuliana,Bovicelli, Paolo,Sperandio, Anna
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- α-Bromination of linear enals and cyclic enones
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Facile α-bromination of cyclic enones and linear enals involving N-bromosuccinimide and 1-2 equiv of pyridine-N-oxide is reported herein. α-Bromination of linear enals was found to proceed with double bond geometry retention.
- Bovonsombat, Pakorn,Rujiwarangkul, Rungkarn,Bowornkiengkai, Thanathip,Leykajarakul, Juthamard
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- Synthesis of novel methyl jasmonate derivatives and evaluation of their biological activity in various cancer cell lines
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Warburg hypothesized that the energy consumption of cancer cells is different than the normal cells. When compared to normal conditions, cancer cells do not undergo tricarboxylic acid (TCA) cycle therefore resulting in more lactate in the cells. Glycolysis pathway is a way of cancer cells to provide energy. The first step in glycolysis is the phosphorylation of glucose to glucose-6-phosphate. This reaction is catalyzed by the hexokinase-II enzyme (HK-II) which is known to be overexpressed in tumor cells. The feeding of cancer cells can be prevented by inhibiting the hexokinase-II enzyme in the first step of aerobic glycolysis. In literature, Methyl Jasmonate (MJ) is known as a Hexokinase-II inhibitor since it disposes VDAC and HK-II interaction on mitochondrial membrane. In our study, we aimed to increase the activity by synthesizing the novel MJ analogues with appropriate modifications. Here we report Hexokinase-2 enzyme and cell viability study results in different cancer cells. Based on the three different cancer cell lines we investigated, our novel MJ analogues proved to be more potent than the original molecule. Thus this research may provide more efficacious/novel HK-II inhibitors and may shed light to develop new anti-cancer agents.
- Sucu, Bilgesu Onur,Ipek, Ozgecan Savlug,Kurtulus, Sukran Ozdatli,Yazici, Busra Emine,Karakas,Guzel, Mustafa
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- Synthesis of ACE tricyclic systems of daphnicyclidin A and dehy-droxymacropodumine A
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The synthesis of the ACE tricyclic system of daphnicyclidin A and dehydroxymacropodumine A are developed. The key reactions include an efficient aldol reaction to introduce chiral fragment 33 for further construction of piperidine ring B and seven-membered ring C, a nucleophilic addition of lithium pentene to aldehyde for installation of ring E, and a photocatalytic decarboxylation conjugate addition to construct ring C.
- Wang, Qi,Zhang, Chao,Yang, Jun
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supporting information
p. 1906 - 1910
(2019/12/27)
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- Sequential O-Arylation/Lanthanide(III)-Catalyzed [3,3]-Sigmatropic Rearrangement of Bromo-Substituted Allylic Alcohols
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Lanthanide(III)-catalyzed aryl-Claisen rearrangement of substrates bearing halo-substituted allyl groups, specifically 2-bromoallyl aryl ethers, afford ortho -2-bromoallylphenols. Aryl ether substrates were synthesized from brominated allylic alcohols via Mitsunobu reaction, Cu(II)-catalyzed arylation using potassium aryltrifluoroborate salts, or S N Ar reaction. Aryl-Claisen rearrangements proceeded in moderate to excellent yields using Eu(III) catalysis. The alkenylbromide functionality remains intact, illustrating the compatibility of synthetically important alkenylhalides during C-O/C-C σ-bond migration processes. Subsequent derivatization of the ortho -2-bromoallylphenol products through O-alkylation or C-arylation/alkenylation via Suzuki-Miyaura cross-coupling demonstrate the potential to access densely-functionalized molecules.
- Ramadhar, Timothy R.,Kawakami, Jun-Ichi,Batey, Robert A.
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supporting information
p. 2865 - 2870
(2017/12/14)
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- Substituted Imidazopyridines as HDM2 Inhibitors
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The present invention provides substituted imidazopyridines as described herein or a pharmaceutically acceptable salt or solvate thereof. The representative compounds are useful as inhibitors of the HDM2 protein. Also disclosed are pharmaceutical compositions comprising the above compounds and potential methods of treating cancer using the same.
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Paragraph 0805
(2014/07/08)
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- 1,4-Benzothiazine ATP-sensitive potassium channel openers: Modifications at the C-2 and C-6 positions
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ATP-sensitive potassium (KATP) channels play a prominent role in controlling cardiovascular function. In this paper, a novel series of 4-(1-oxo-2-cyclopentenyl)-1,4-benzothiazine derivatives modified at the C-2, and C-6 positions were synthesized as openers of vascular KATP channels. Most of the tested compounds evoked vasorelaxing effects on rat aortic rings and membrane hyperpolarization in human vascular smooth muscle cells, with potency similar or superior to that of the reference levcromakalim (LCRK). The selective KATP blocker glibenclamide antagonized the above vascular effects, confirming that KATP channels are closely involved in the mechanism of action. The experimental results confirmed the 1,4-benzothiazine nucleus as an optimal scaffold for activators of vascular KATP channels; moreover, the high level of potency exhibited by the 6-acetyl substituted benzothiazine 8, along with the lack of any significant interference with insulin secretion from pancreatic β-cells, paves the way to further develop a new series of potent activators of vascular KATP channels.
- Martelli, Alma,Manfroni, Giuseppe,Sabbatini, Paola,Barreca, Maria Letizia,Testai, Lara,Novelli, Michela,Sabatini, Stefano,Massari, Serena,Tabarrini, Oriana,Masiello, Pellegrino,Calderone, Vincenzo,Cecchetti, Violetta
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p. 4718 - 4728
(2013/07/19)
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- Reactivity and stereoselectivity of the Diels-Alder reaction using cyclic dienophiles and siloxyaminobutadienes
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Several bicyclic compounds were synthesized by the Diels-Alder reaction using aminodiene and a cyclic dienophile. The stereochemistries of the obtained adducts were determined by X-ray crystallography or NMR analysis. The stereoselectivity of this Diels-A
- Ohfusa, Toshiyuki,Nishida, Atsushi
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experimental part
p. 1893 - 1906
(2011/04/17)
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- Enantioselective, biocatalytic reduction of 3-substituted cyclopentenones: Application to the asymmetric synthesis of an hNK-1 receptor antagonist
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A convergent and enantioselective route to the hNK-1 receptor antagonist (1) is described, which sets all six stereogenic centers with high diastereoselectivity and delivers 1 in only 11 steps and 23% overall yield. The process was enabled by the developm
- Campos, Kevin R.,Klapars, Artis,Kohmura, Yoshinori,Pollard, David,Ishibashi, Hideaki,Kato, Shinji,Takezawa, Akihiro,Waldman, Jacob H.,Wallace, Debra J.,Chen, Cheng-Yi,Yasuda, Nobuyoshi
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supporting information; experimental part
p. 1004 - 1007
(2011/05/08)
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- Intramolecular Simmons-Smith cyclopropanation. Studies into the reactivity of alkyl-substituted zinc carbenoids, effect of directing groups and synthesis of bicyclo[n.1.0]alkanes
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An intramolecular Simmons-Smith (IMSS) cyclopropanation has been developed, providing a novel method for the construction of substituted bicycloalkanes. First, functionalized gem-diiodoalkanes containing allylic alcohols were prepared in high yield. Then
- Bull, James A.,Charette, Andre B.
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supporting information; scheme or table
p. 1895 - 1902
(2010/04/25)
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- Cascade palladium-catalyzed direct intramolecular arylation/alkene isomerization sequences: Synthesis of indoles and benzofurans
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One route, two cycles: A palladium-catalyzed intramolecular direct arylation reaction combined with an isomerization step provided a straightforward synthetic route to both indoles and benzofurans (see scheme). Isolation and functionalization of intermedi
- Yagoubi, Myriam,Cruz, Ana C. F.,Nichols, Paula L.,Elliott, Richard L.,Willis, Michael C.
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supporting information; experimental part
p. 7958 - 7962
(2011/01/11)
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- Highly enantioselective and regioselective carbonyl reduction of cyclic α,β-unsaturated ketones using TarB-N02 and sodium borohydride
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Asymmetric 1,2-reduction of α,β-unsaturated ketones using TarB-NO2 and NaBH4 Is reported. Simple cycloalkenones give products In low enantiomeric excess. However, cycloalkenones with a-substituents, such as halides, alkyl, and aryl, have been enantioselectively reduced with this system to yield chiral allylic alcohols In enantiomeric excess up to 99%. The starting materials for TarB-N02 are inexpensive, and the boronlc acid can be easily recovered In high yield by a simple acid extraction.
- Kim, Jinsoo,Bruning, John,Park, Kevin E.,Lee, David J.,Singaram, Bakthan
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supporting information; experimental part
p. 4358 - 4361
(2009/12/24)
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- The palladium-catalyzed aerobic kinetic resolution of secondary alcohols: Reaction development, scope, and applications
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The first palladium-catalyzed enantioselective oxidation of secondary alcohols has been developed, utilizing the readily available diamine (-)-sparteine as a chiral ligand and molecular oxygen as the stoichiometric oxidant. Mechanistic insights regarding the role of the base and hydrogen-bond donors have resulted in several improvements to the original system. Namely, addition of cesium carbonate and tert-butyl alcohol greatly enhances reaction rates, promoting rapid resolutions. The use of chloroform as solvent allows the use of ambient air as the terminal oxidant at 23°C, resulting in enhanced catalyst selectivity. These improved reaction conditions have permitted the successful kinetic resolution of benzylic, allylic, and cyclopropyl secondary alcohols to high enantiomeric excess with good-toexcellent selectivity factors. This catalyst system has also been applied to the desymmetrization of meso-diols, providing high yields of enantioenriched hydroxyketones.
- Ebner, David C.,Bagdanoff, Jeffrey T.,Ferreira, Eric M.,McFadden, Ryan M.,Caspi, Daniel D.,Trend, Raissa M.,Stoltz, Brian M.
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supporting information; experimental part
p. 12978 - 12992
(2010/06/19)
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- PROCESS FOR MAKING LACTAM TACHYKININ RECEPTOR ANTAGONISTS
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The present invention is directed to a process for preparing certain α,α disubstituted γ-lactam derivatives that are useful as neurokinin-1 (NK-1) receptor antagonists, and inhibitors of tachykinin and in particular substance P. The compounds are useful i
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Page/Page column 40; 55-56
(2008/06/13)
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- Thermal intramolecular Diels-Alder reaction of furan; synthesis of nitrogen tetracycles, isobenzofuran and isobenzothiophene
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Thermal intramolecular Diels-Alder (IMDA) reaction of furan cored compounds has been further investigated; a series of key precursors to the IMDA reaction of furan diene (9a-c) have been prepared via facile alkylation and protection. While the cycloadditi
- Karaarslan, Muhsin,Gokturk, Ersen,Demircan, Aydin
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p. 117 - 120
(2008/02/02)
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- Synthesis and stereochemical confirmation of the secoiridoid glucosides nudiflosides D and A
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We describe herein an efficient access to the highly substituted cyclopentane unit present in the Nudifloside secoiridoid family via crotyl phosphonamide anion mediated conjugate addition to cyclopentenone.
- Hanessian, Stephen,Mainetti, Emily,Lecomte, Fabien
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p. 4047 - 4049
(2007/10/03)
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- 4-(2-Methyl-5,6,7,8-tetrahydro-quinolin-7-ylmethyl)-1,3-dihydro-imidazole-2-thione as specific alpha2B agonist and methods of using the same
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The compound of the formula wherein the * indicates an asymmetric carbon, is specific to alpha2B adrenergic receptors in preference over alpha2A and alpha2C adrenergic receptors, and as such has no or only minimal cardivascular and/or sedatory activity. The compound is useful as medicament in mammals, including humans, for treatment of diseases and or alleviations of conditions which are responsive to treatment by agonists of alpha2B adrenergic receptors.
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- Anti-ischemic compounds
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The present invention is related to a compound of formula (I), salts and pro-drugs of the compound (I) and methods for treating and/or preventing partial or total ischemia, methods for treating and/or preventing pathologies associated with ischemia or with mitochondrial deficiencies.
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- Structure-dependent oxidative bromination of unsaturated C-C bonds mediated by selectfluor
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A number of olefins were subjected to oxidative bromination using Selectfluor/KBr. For different types of substrates, addition, monobromine-substituted, or Hunsdiecker-Borodin reaction products can be readily afforded.
- Ye, Chengfeng,Shreeve, Jean'Ne M.
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p. 8561 - 8563
(2007/10/03)
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- 4-(substituted cycloalkylmethyl) imidazole-2-thiones, 4-(substituted cycloalkenylmethyl) imidazole-2-thiones, 4-(substituted cycloalkylmethyl) imidazol-2-ones and 4-(substituted cycloalkenylmethyl) imidazol-2-ones and related compounds
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Compounds of Formula 1 where X is S and the variables have the meaning defined in the specification are specific or selective to alpha2B and/or alpha2C adrenergic receptors in preference over alpha2A adrenergic receptors, and as such have no or only minimal cardivascular and/or sedatory activity. These compounds of Formula 1 are useful as medicaments in mammals, including humans, for treatment of diseases and or alleviations of conditions which are responsive to treatment by agonists of alpha2B adrenergic receptors. Compounds of Formula 1 where X is O also have the advantageous property that they have no or only minimal cardivascular and/or sedatory activity and are useful for treating pain and other conditions with no or only minimal cardivascular and/or sedatory activity.
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- 4-SUBSTITUTED IMIDAZOLE-2-THIONES AND IMIDAZOL- 2-ONES AS AGONISTS OF THE ALPHA- 2B AND ALPHA-2C ADRENERGIC RECEPTORS
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Compounds of Formula (I): where X is S and the variables have the meaning defined in the specification are specific or selective to alpha2B and/or alpha2C adrenergic receptors in preference over alpha2A adrenergic receptors, and as such have no or only minimal cardivascular and/or sedatory activity. These compounds of Formula (I) are useful as medicaments in mammals, including humans, for treatment of diseases and or alleviations of conditions which are responsive to treatment by agonists of alpha2B adrenergic receptors. Compounds of Formula (I) where X is O also have the advantageous property that they have no or only minimal cardivascular and/or sedatory activity and are useful for treating pain and other conditions with no or only minimal cardivascular and/or sedatory activity.
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- A convenient and useful method of preparation of α-bromo enones from the corresponding enones using organic ammonium tribromide (OATB)
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Various acyclic α-bromo enones 2 as well as cyclic α-bromo enones 4 can be prepared from the corresponding acyclic enones 1 and cyclic enones 3 respectively, in a one-pot procedure by employing organic ammonium tribromide, such as cetyltrimethylammonium t
- Bose, Gopal,Bujar Barua, Pankaj M.,Chaudhuri, Mihir K.,Kalita, Dipak,Khan, Abu T.
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p. 290 - 291
(2007/10/03)
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- A radical based addition-elimination route for the preparation of indoles
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Indoles, including tricyclic derivatives, are produced by cyclisations of aryl radicals onto vinyl halides followed by elimination of halide radical and tautomerism of the resulting product; the aryl radicals are produced using "clean methodology" either by reaction of iodide ions with arenediazonium salts or by reaction of phosphorus-centred radicals with aryl iodides. The Royal Society of Chemistry 2000.
- Murphy, John A.,Scott, Karen A.,Sinclair, Rhoha S.,Martin, Concepcion Gonzalez,Kennedy, Alan R.,Lewis, Norman
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p. 2395 - 2408
(2007/10/03)
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- Pyridinyl-2-cyclopenten-1-ones as selective cyclooxygenase-2 inhibitors
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The invention encompasses the novel compound of Formula I as well as a method of treating COX-2 mediated diseases comprising administration to a patient in need of such treatment of a non-toxic therapeutically effective amount of a compound of Formula I.
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- Solvent-free organic reactions on silica gel supports. Facile transformation of epoxides to β-halohydrins with lithium halides
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The reaction of epoxides with lithium halides was efficiently promoted on the surface of silica gel in the absence of any solvent to give the corresponding β-halohydrins. The reactivity of lithium halides was shown to follow the order LiI > LiBr >> LiCl, and the reactivity of LiCl was dramatically increased by adding an equivalent amount of water to this system. On the other hand a similar reaction with α,β-epoxyketones produces the α-haloenone derivatives, presumably via halohydrin intermediates. The epoxide-opening reaction of (R)-(+)-styrene oxide was also investigated to clarify the stereochemical features of this reaction.
- Kotsuki, Hiyoshizo,Shimanouchi, Tomoyasu,Ohshima, Reiji,Fujiwara, Shunsuke
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p. 2709 - 2722
(2007/10/03)
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- 2-(3,5-difluorophenyl)-3-(4-(methyl-sulfonyl)phenyl)-2-cyclopenten-1-one useful as an inhibitor of cyclooxygenase-2
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The invention encompasses the novel compound A, 2-(3,5-difluorophenyl)-3-(4-(methylsulfonyl)phenyl)-2-cyclopenten-1-one, pharmaceutical compositions and use of the compound in the preparation of medicaments for the treatment of cyclooxygenase-2 mediated diseases.
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- 3,4-diaryl-2-hydroxy-2,5-dihydrofurans as prodrugs to COX-2 inhibitors
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The invention encompasses the novel compound of Formula I useful in the treatment of cyclooxygenase-2 mediated diseases. STR1 The invention also encompasses certain pharmaceutical compositions for treatment of cyclooxygenase-2 mediated diseases comprising compounds of Formula I.
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- An Attempted Synthesis of 1,2-Cyclopentadiene and Wurtz-Like Condensation Products in the Reaction of 1,2-Dibromocycloalkenes
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Fluoride ion-promoted elimination of 2-bromo-3-trimethylsilyl cyclohexene 16 and 2-bromo-3-trimethylsilyl cycloheptene 17 has been successfully used for synthesis of strained six- and seven- membered cyclic allenes.When 2-bromo-3-trimethylsilyl cyclopentene 5 was submitted to fluoride ion-promoted elimination only Wurtz-like dimeric products 6 and 7 were obtained instead of the expected 1,2-cyclopentadiene 8.Interestingly, reaction of 2,3-dibromocyclopentene 4, 2,3-dibromocyclohexene 12, and 2,3-dibromocycloheptene 13 with zinc gave only Wurtz-like dimeric products, (6,7), (18,19) and (20,21), respectively.
- Ceylan, Mustafa,Secen, Hasan,Sutbeyaz, Yaser
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p. 501 - 508
(2007/10/03)
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- Transition Metal Promoted Acetylene Isomerisation Reactions In Organic Synthesis
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A transition metal mediated acetylene-vinylidene rearrangement has been developed for the synthesis of spirocyclic lactones
- Quayle, Peter,Rahman, Shopna,Ward, E. Lucy M.,Herbert, John
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p. 3801 - 3804
(2007/10/02)
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- The Synthesis and Chemistry of A Simplified, Functional Analogue of Neocarzinostatin Chromophore: Identification of an Intramolecular 1,5-Hydrogen Atom Transfer Relevant to the Mechanism and Cleavage Selectivity of Diyl-Based DNA Cleaving Agents
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The synthesis and chemistry of a monocyclic analogue of neocarzinostatin chromophore are described.This analogue is activated through a Michael addition process and provides cycloaromatized products similar to those obtained in the activation of neocarzinostatin chromophore.Mechanistic studies on this analogue have led to the first identification of a diyl self-quenching pathway based on a 1,5-hydrogen atom transfer that provides a novel hypothesis about the relationship between thiol structure and DNA single and double strand cleavage selectivity for neocarzinostatin chromophore and diyl-based cleaving agents.
- Wender, Paul A.,Tebbe, Mark J.
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p. 1419 - 1434
(2007/10/02)
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- Enantioselective Total Synthesis of Ginkgolide Derivatives Lacking the tert-Butyl Group, an Essential Structural Subunit for Antagonism of Platelet Activating Factor
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An enantioselective total synthesis of the ginkgolide B analog 3 is reported along with results of bioassays for antagonism of platelet activating factor.The three orders of magnitude difference in bioactivity of 2 and 3 demonstrates that the tert-butyl group of the ginkgolides is essential for anti-PAF potency.
- Corey, E. J.,Rao, K. Srinivas
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p. 4623 - 4626
(2007/10/02)
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- Preparation of chiral allylic alcohols using Rhizopus nigricans. Use of the Harada-Nakanishi exciton chirality method for verifying configurational assignments of allylic alcohols
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A series of (R) acyclic and cyclic allylic alcohols was prepared by enantioselective hydrolysis of acetates using Rhizopus nigricans.The configurations of the alcohols formed were established by chemical methods and, in the case of 1,2-benzocyclohepta-1,3
- Ito, Satoru,Kasai, Masaji,Ziffer, Herman,Silverton, J.V.
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p. 574 - 582
(2007/10/02)
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- Synthetic Elaboration of Diosphenols: Replacement of Hydroxyl by Halogen
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Replacement of the enolic oxygen of diosphenols by chlorine or bromine may be achieved by treating the derived dimethylthiocarbamate with lithium chloride or bromide in hot acetonitrile/acetic acid.
- Ponaras, Anthony A.,Zaim, Oemer
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p. 4741 - 4743
(2007/10/02)
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- Reactions of α-Diazo Ketones with Selenium-based Reagents. A General Synthesis of α-Chloro-, α-Bromo, α-Phenylseleno-, α-Acetoxy-, and α-Methoxy-αβ-unsaturated Ketones
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Benzeneselenenyl derivatives, PhSe-X (X=Cl, Br, OCOCH3, and SCN) react readily with α-diazo ketones, RCOC(N2)R1 (R1=H or alkyl), with loss of nitrogen, furnishing αα-adducts of the type RCOCR1(X)SePh.The α-chloro and α-bromo adducts can be converted into α-methoxy adducts in methanol-sodium hydrogen carbonate.The utility of these adducts in synthesis is illustrated by their conversion (where structural considerations permit) via selenoxide fragmentation into α-heterosubstituted αβ-unsaturated ketones.Treatment of the series RCOCR1(X)SePh (R1=alkyl; X=Cl, Br, OCOCH3, and OCH3) with hydrogen peroxide-pyridine produces α-chloro-, α-bromo-, α-acetoxy-, and α-methoxy-αβ-unsaturated ketones, whereas treatment of series RCOCR1(X)SePh (R1=alkyl; X=Cl and Br) with lithium carbonate in dimethylformamide produces α-phenylseleno-αβ-unsaturated ketones.Several α-substituted cyclopentenones, cyclohexenones, and cycloheptenones have been synthesised in this way and acyclic examples are illustrated by the synthesis of 3-chloro-, 3-bromo-, 3-acetoxy-, 3-methoxy,-and 3-phenylselenobut-3-en-2-one from 3-diazobutan-2-one.
- Buckley, Daniel J.,McKervey, M. Anthony
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p. 2193 - 2200
(2007/10/02)
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- α-Keto Dianion Precursors via Conjugate Additions to Cyclic α-Bromo Enones
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Successful conjugate to 2-bromocyclohexenone and 2-bromocyclopentenone have been achieved with a variety of lithium homocuprates, mixed cyanocuprates, and lithium tri-sec-butylborohydride as well.In all cases the resulting α-bromo enolate anions could be
- Kowalski, Conrad J.,Weber, Ann E.,Fields, Kevin W.
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p. 5088 - 5093
(2007/10/02)
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- The electrophilic addition of dimethylbromosulfonium bromide to conjugated enones: efficient synthesis of α-bromo enones
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Dimethylbromosulfonium bromide reacted readily with many enones at 0 deg C or lower to precipitate α-bromo-β-sulfonium conjugated enones.These salts eliminate a proton and dimethylsulfide readily with aqueous potassium carbonate to give excellent yields o
- Chow, Yuan L.,Bakker, Bert H.
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p. 2268 - 2273
(2007/10/02)
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- A CONVENIENT PREPARATION OF 2-HALOENONES FROM ENONES USING PHENYLSELENIUM HALIDES
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Enones can be converted in high yield to their corresponding 2-halo analogues by treatment with an excess of phenylselenium halide in methylene chloride/pyridine at 37 deg C.
- Ley, Steven V.,Whittle, Alan J.
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p. 3301 - 3304
(2007/10/02)
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