- Generation of Acyl Radical Equivalents by Cathodic Reduction of Acyl Tributylphosphonium Ions
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The species generated by one-electron transfer to acyl tributylphosphonium ions has proved to be potent acyl radical equivalents by the results that unsubstituted and 6-phenyl- substituted 5-hexenoic acids were transformed into cyclopentanones by the electrolysis in the presence of Bu3P in an undivided cell, although the yields were not satisfactory due to the formation of 5-hexen-1-als via further one-electron reduction of the radicals before their cyclization.
- Maeda, Hatsuo,Maki, Toshihide,Ohmori, Hidenobu
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- Tetrabutylammonium difluorotriphenylstannate [Bu4N][Ph 3SnF2]: Delivering carbon or fluorine ligands via hypercoordination
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The reagent, tetrabutylammonium difluorotriphenylstannate, was easily prepared on a multigram scale (~100 g). Several of its applications are presented, either as a soluble, thermally stable and anhydrous nucleophilic fluorinating agent or as a synthetic equivalent to PhMgX or PhLi species under aqueous and aerobic conditions. The proposed methodologies emphasize the concept of hypercoordination and its usefulness for improving selectivity, reactivity and shelf-stability of reagents. Georg Thieme Verlag Stuttgart.
- Gingras, Marc,Chabre, Yoann M.,Raimundo
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- Substituted cyclopropylamines from pyridinium ylide: Complexes of pentacarbonyl tungsten and enamines
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Enamines derived from cyclic ketones react very easily with a series of pyridinium ylide complexes of tungsten pentacarbonyl (CO)5W--C(R)(H) Py+ to give either at room temperature (for R = Ph) or at 40°C (for R = alkyl) substituted cyclopropylamines as mixtures of stereoisomers.
- Martin-Vaca, Bianca,Durand-Reville, Thomas,Audouin, Max,Rudler, Henri
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- INHIBITORS OF NOROVIRUS AND CORONAVIRUS REPLICATION
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Compounds of Formula (I) and methods of inhibiting the replication of viruses in a biological sample or patient, of reducing the amount of viruses in a biological sample or patient, and of treating a virus infection in a patient, comprising administering to said biological sample or patient an effective amount of a compound represented by Formula (I), a compound of Table A or B or a pharmaceutically acceptable salt thereof.
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Paragraph 00600; 00603-00604; 00684; 00687-00688
(2021/10/15)
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- A Proton-Responsive Pyridyl(benzamide)-Functionalized NHC Ligand on Ir Complex for Alkylation of Ketones and Secondary Alcohols
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A Cp*Ir(III) complex (1) of a newly designed ligand L1 featuring a proton-responsive pyridyl(benzamide) appended on N-heterocyclic carbene (NHC) has been synthesized. The molecular structure of 1 reveals a dearomatized form of the ligand. The protonation of 1 with HBF4 in tetrahydrofuran gives the corresponding aromatized complex [Cp*Ir(L1H)Cl]BF4 (2). Both compounds are characterized spectroscopically and by X-ray crystallography. The protonation of 1 with acid is examined by 1H NMR and UV-vis spectra. The proton-responsive character of 1 is exploited for catalyzing α-alkylation of ketones and β-alkylation of secondary alcohols using primary alcohols as alkylating agents through hydrogen-borrowing methodology. Compound 1 is an effective catalyst for these reactions and exhibits a superior activity in comparison to a structurally similar iridium complex [Cp*Ir(L2)Cl]PF6 (3) lacking a proton-responsive pendant amide moiety. The catalytic alkylation is characterized by a wide substrate scope, low catalyst and base loadings, and a short reaction time. The catalytic efficacy of 1 is also demonstrated for the syntheses of quinoline and lactone derivatives via acceptorless dehydrogenation, and selective alkylation of two steroids, pregnenolone and testosterone. Detailed mechanistic investigations and DFT calculations substantiate the role of the proton-responsive ligand in the hydrogen-borrowing process.
- Kaur, Mandeep,U Din Reshi, Noor,Patra, Kamaless,Bhattacherya, Arindom,Kunnikuruvan, Sooraj,Bera, Jitendra K.
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supporting information
p. 10737 - 10748
(2021/06/15)
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- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Chemoselective and metal-free reduction of α,β-unsaturated ketones by: In situ produced benzeneselenol from O -(tert -butyl) Se-phenyl selenocarbonate
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The carbon-carbon double bond of arylidene acetones and chalcones can be selectively reduced with benzeneselenol generated in situ by reacting O-(tert-butyl) Se-phenyl selenocarbonate with hydrochloric acid in ethanol. This mild, metal-free and experimentally simple reduction procedure displays considerable functional-group compatibility, products are obtained in good to excellent yields, and the use of toxic Se/CO mixture and NaSeH, or the smelly and air-sensitive benzeneselenol, is avoided. This journal is
- Ballarotto, Marco,Siciliano, Carlo,Temperini, Andrea
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p. 33706 - 33717
(2020/10/22)
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- Synthesis and structural characterization of facile ruthenium(II) hydrazone complexes: Efficient catalysts in α-alkylation of ketones with primary alcohols via hydrogen auto transfer
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As a immersion for development of new complexes, new Ru(II) complexes (1–3) supported by benzothiazole hydrazine Schiff bases of the type [Ru(SAL-HBT)(CO)(AsPh3)2], [Ru(VAN-HBT)(CO)(AsPh3)2] and [Ru(NAP-HBT)(CO)Cl(AsPh3)2] [SAL-HBT = (salicyl((2-(benzothiazol-2yl)hydrazono)methylphenol)), VAN-HBT = 2-((2-(benzothiazol-2-yl)hydrazono)methyl)-6 methoxyphenol) and NAP-HBT = naphtyl-2-((2-(benzothiazol-2-yl)hydrazono)methyl phenol)] were synthesized. Their identities have been established by satisfactory elemental analyses, various spectroscopic techniques (IR, (1H, 13C) NMR) and also mass spectrometry. The ruthenium(II) ion exhibits a hexa coordination with distorted octahedral geometry. In complexes 1 and 2, the ligand coordinated as dianionic tridentate fashion by forming N^N donor five member and N^O donor six member chelate rings. However, in complex 3, the ligand coordinated as monoanionic bidentate fashion by forming N^N donor five-membered ring. The new ruthenium(II) carbonyl complexes were successfully applied as catalysts in α -alkylation of aliphatic and aromatic ketones with alcohols via borrowing hydrogen strategy. Various parameters such as base, solvent, temperature, time and catalyst loading on the catalytic activity were analyzed. From the results, the catalyst 1 was found to be the best catalyst for α-alkylation reaction to obtain excellent yield. The catalytic system has a broad substrate scope, which allows the synthesis of α-alkylated ketones in mild reaction conditions with low catalyst loading under air atmosphere.
- Kalaiarasi, Chinnasamy,Murugan, Kaliyappan,Vijayan, Paranthaman,Vijayapritha, Subbarayan,Viswanathamurthi, Periasamy
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supporting information
(2020/08/06)
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- A substituted phenylacetic acid derivatives (by machine translation)
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The invention belongs to the field of drug synthesis, relates to a substituted phenylacetic acid derivatives, in particular to the preparation of 2 - [4 - (2 - methyl oxygen fifth heavenly stem) hydrocinnamic acid] preparation method. If nitrile alkylation reaction include alkylation reaction, reaction or ester alkyl [...] reaction to prepare the intermediate type II - 2 or type II - 2' compound, After the hydrolytic reaction or oxidation reaction preparation to obtain the product. The invention relates to the alkylation reaction without additional solvent, is a more industrialization of the advantages of the line. (by machine translation)
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Paragraph 0043; 0044
(2019/04/18)
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- Iron-Catalyzed Ligand Free α-Alkylation of Methylene Ketones and β-Alkylation of Secondary Alcohols Using Primary Alcohols
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Herein, we demonstrate a general and broadly applicable catalytic cross coupling of methylene ketones and secondary alcohols with a series of primary alcohols to disubstituted branched ketones. A simple and nonprecious Fe2(CO)9 catalyst enables one-pot oxidations of both primary and secondary alcohols to a range of branched gem-bis(alkyl) ketones. A number of bond activations and formations selectively occurred in one pot to provide the ketone products. Coupling reactions can be performed in gram scale and successfully applied in the synthesis of an Alzehimer's drug. Alkylation of a steroid hormone can be achieved. A single catalyst enables sequential one-pot double alkylation to bis-hetero aryl ketones using two different alcohols. Preliminary mechanistic studies using an IR probe, deuterium labeling, and kinetic experiments established the participation of a borrowing-hydrogen process using Fe catalyst, and the reaction produces H2 and H2O as byproducts.
- Alanthadka, Anitha,Bera, Sourajit,Banerjee, Debasis
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p. 11676 - 11686
(2019/10/02)
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- Nickel-Catalyzed Hydrogen-Borrowing Strategy for α-Alkylation of Ketones with Alcohols: A New Route to Branched gem-Bis(alkyl) Ketones
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The α-alkylation of ketones using an earth-abundant and nonprecious NiBr2/L1 system is reported. This nickel-catalyzed reaction could be performed in gram scale and successfully applied in the synthesis of donepezil (Alzheimer's drug) and functionalization of steroid hormones and fatty acid derivatives. Synthesis of N-heterocycles, methylation of ketones, and one-pot double alkylation to bis-hetero aryl ketones using two different alcohols with a single catalyst broadens the scope of the catalytic protocol. Preliminary mechanistic studies using defined Ni-H species and deuterium-labeling experiments established the participation of the borrowing-hydrogen strategy.
- Das, Jagadish,Singh, Khushboo,Vellakkaran, Mari,Banerjee, Debasis
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supporting information
p. 5587 - 5591
(2018/09/25)
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- RhCl(CO)(PPh3)2 catalyzed α-alkylation of ketones with alcohols
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A simple and efficient method for α-alkylation of ketones with primary alcohols catalyzed by RhCl(CO)(PPh3)2 without additional additives under mild conditions is developed. It has a wide substrate scope, high atom-efficiency and chemoselectivity. It is an environmentally friendly method to build C[sbnd]C bond because water is the only byproduct.
- Wang, Rui,Huang, Lina,Du, Zhengyin,Feng, Hua
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supporting information
p. 40 - 43
(2017/06/07)
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- Reactivity of Lithium β-Ketocarboxylates: The Role of Lithium Salts
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Lithium β-ketocarboxylates 1(COOLi), prepared by the reaction of lithium enolates 2(Li+) with carbon dioxide, readily undergo decarboxylative disproportionation in THF solution unless in the presence of lithium salts, in which case they are indefinitely stable at room temperature in inert atmosphere. The availability of stable THF solutions of lithium β-ketocarboxylates 1(COOLi) in the absence of carbon dioxide allowed reactions to take place with nitrogen bases and alkyl halides 3 to give α-alkyl ketones 1(R) after acidic hydrolysis. The sequence thus represents the use of carbon dioxide as a removable directing group for the selective monoalkylation of lithium enolates 2(Li+). The roles of lithium salts in preventing the disproportionation of lithium β-ketocarboxylates 1(COOLi) and in determining the course of the reaction with bases and alkyl halides 3 are discussed.
- Berton, Mateo,Mello, Rossella,Williard, Paul G.,González-Nú?ez, María Elena
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supporting information
p. 17414 - 17420
(2017/12/15)
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- Unexpected metal-free transformation of gem-dibromomethylenes to ketones under acetylation conditions
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Novel conditions for the transformation of gem-dibromomethylenes to ketones are described. gem-Dibromo compounds were treated with acetic anhydride and triethylamine in dichloromethane/water at room temperature under an air atmosphere to give the corresponding ketones in moderate yields. A radical mechanism is proposed based on experimental results.
- Kimura, Rino,Sawayama, Yusuke,Nakazaki, Atsuo,Miyamoto, Kazunori,Uchiyama, Masanobu,Nishikawa, Toshio
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p. 1035 - 1041
(2015/03/31)
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- Regio- and enantioselective Baeyer-Villiger oxidation: Kinetic resolution of racemic 2-substituted cyclopentanones
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A kinetic resolution of racemic 2-substituted cyclopentanones via highly regio- and enantioselective Baeyer-Villiger oxidation has been successfully developed. The reaction could afford the normal 6-substituted δ-lactones in up to 98% ee and >19/1 regioselectivity. Meanwhile, the unreacted ketones were recovered in excellent ee values (up to 98%). It represents the best results of the kinetic resolution of racemic 2-substituted cyclopentanones via nonenzymic asymmetric BV oxidation.
- Zhou, Lin,Liu, Xiaohua,Ji, Jie,Zhang, Yuheng,Wu, Wangbin,Liu, Yangbin,Lin, Lili,Feng, Xiaoming
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supporting information
p. 3938 - 3941
(2014/08/18)
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- One-pot β-alkylation of secondary alcohols with primary alcohols catalyzed by ruthenacycles
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A ruthenacycle-catalyzed one-pot β-alkylation of secondary alcohols with primary alcohols is described. A survey of four C-N chelate ruthenacycles synthesized via the cyclometallation reaction of phenylmethanamine, N-methylphenylmethanamine, N,N-dimethylphenylmethanamine, and naphthalen-1-ylmethanamine with [(η6-C6H 6)RuCl2]2 was undertaken. All four complexes were found to be active with the phenylmethanamine-based ruthenacycle showing the best combination of reactivity and product selectivity among the four. An expanded scope of substrates was also studied with the inclusion of unsaturated primary alcohols. The reactivity trend observed gave insights into the role of hydrogen bonding in the catalytic mechanism involving transfer hydrogenation between the substrates and the transition metal catalyst.
- Chang, Xu,Chuan, Low Wei,Yongxin, Li,Pullarkat, Sumod A.
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experimental part
p. 1450 - 1455
(2012/04/10)
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- Carbamoyloximes as novel non-competitive mGlu5 receptor antagonists
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Hit-to-lead optimization of a HTS hit led to new carbamoyloxime derivatives. After identification of an advanced hit (8d) the CYP enzyme inhibitory activity of this class of compounds was successfully eliminated. Systematic exploration of different parts of the advanced hit led us to some promising lead compounds with mGluR5 affinities comparable to that of MPEP.
- Galambos, Janos,Wagner, Gabor,Nogradi, Katalin,Bielik, Attila,Molnar, Laszlo,Bobok, Amrita,Horvath, Attila,Kiss, Bela,Kolok, Sandor,Nagy, Jozsef,Kurko, Dalma,Bakk, Monika L.,Vastag, Monika,Saghy, Katalin,Gyertyan, Istvan,Gal, Krisztina,Greiner, Istvan,Szombathelyi, Zsolt,Keser, Gyoergy M.,Domany, Gyoergy
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scheme or table
p. 4371 - 4375
(2010/10/02)
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- New cyclopentane derivatives as inhibitors of steroid metabolizing enzymes AKR1C1 and AKR1C3
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A series of cyclopentane derivatives was synthesized and evaluated for inhibition of the steroid metabolizing enzymes AKR1C1 and AKR1C3. Selective inhibitors that are active in the low micromolar range were identified. These compounds represent promising starting points in the development of new anticancer agents for the treatment of hormone-dependent forms of cancer and other diseases where AKR1C1 and AKR1C3 are involved.
- Stefane, Bogdan,Brozic, Petra,Vehovc, Matej,Rizner, Tea Lanisnik,Gobec, Stanislav
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experimental part
p. 2563 - 2571
(2009/10/17)
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- SmI2-promoted intra- and intermolecular C-C bond formation with chiral N-acyl oxazolidinones
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The suitability of chiral oxazolidinones in the SmI2-mediated C-C bond generation between the imide functionality of an N-acyl oxazolidinone unit and an olefinic radical acceptor, in both inter- and intramolecular reactions, was investigated. It was shown that the products from an Evans asymmetric alkylation can undergo direct carbon-carbon bond formation with an acrylamide providing chiral acyclic ketones in reasonable yields. These examples represent the first transformation of such N-acyl oxazolidinones where this chiral auxiliary is removed under the conditions for ketone formation. 5-exo-trig Cyclization studies were also undertaken with the same type of substrates, providing trans-2,5-disubstituted cyclopentanones in yields of approx. 50%. However, attempts to cyclize heteroatom-containing equivalents were less rewarding.
- Taaning, Rolf H.,Thim, Laura,Karaffa, Jacob,Campa?a, Araceli G.,Hansen, Anna-Mette,Skrydstrup, Troels
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body text
p. 11884 - 11895
(2009/04/07)
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- Ionic liquid as catalyst and solvent: the remarkable effect of a basic ionic liquid, [bmIm]OH on Michael addition and alkylation of active methylene compounds
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A basic ionic liquid, 1-methyl-3-butylimidazolium hydroxide, [bmIm]OH, catalyzes the Michael addition of active methylene compounds to conjugated ketones, carboxylic esters and nitriles. It further catalyzes the addition of thiols to α,β-acetylenic ketones and alkylation of 1,3-dicarbonyl and -dicyano compounds. The Michael addition to α,β-unsaturated ketones proceeds in the usual way, giving the monoaddition products, whereas addition to α,β-unsaturated esters and nitriles leads exclusively to the bis-addition products. The α,β-acetylenic ketones undergo double conjugate addition with thiols producing β-keto 1,3-dithio-derivatives. In the alkylation reaction the acyclic 1,3-diketones are monoalkylated, whereas cyclic ketones undergo dialkylation under identical conditions. All these reactions were carried out without any organic solvent. The ionic liquid can also be recycled.
- Ranu, Brindaban C.,Banerjee, Subhash,Jana, Ranjan
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p. 776 - 782
(2007/10/03)
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- Pd(OAc)2-catalyzed carbonylation of amines
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A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc) 2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N′-dialkylureas were obtained by the carbonylation of primary amines. N,N,N′-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of ω- arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.
- Orito, Kazuhiko,Miyazawa, Mamoru,Nakamura, Takatoshi,Horibata, Akiyoshi,Ushito, Harumi,Nagasaki, Hideo,Yuguchi, Motoki,Yamashita, Satoshi,Yamazaki, Tetsuro,Tokuda, Masao
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p. 5951 - 5958
(2007/10/03)
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- Thiol-catalyzed acyl radical cyclization of alkenals
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(Chemical Equation Presented) Thiol-catalyzed direct generation of acyl radicals and their intramolecular addition to olefins of alkenals gave 2-substituted five- and six-membered cyclic ketones in reasonably good yields. The combination of odorless tert-dodecanthiol and AIBN or V-40 was the initiator of choice among surveyed radical generators for the cyclization of alkenals. Aldehydes having electron-deficient olefins cyclized more easily than those having unactivated olefins.
- Yoshikai, Kazuya,Hayama, Tomoharu,Nishimura, Katsumi,Yamada, Ken-Ichi,Tomioka, Kiyoshi
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p. 681 - 683
(2007/10/03)
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- β elimination of a phosphonate group from an alkoxyl radical - Intramolecular acylation using acylphosphonate derivatives as carbonyl group acceptors
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The possibility of β elimination of a phosphonate group in radical reactions was studied. The facile β elimination of the phosphonate group from an alkoxyl radical was observed for the first time, whereas the β elimination of the phosphonate group from an
- Cho, Chang Ho,Kim, Sunggak
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p. 917 - 921
(2007/10/03)
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- Palladium-catalyzed intramolecular α-arylation of aliphatic ketone, formyl, and nitro groups
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Intramolecular arylation of properly designed substrates bearing a ketone, formyl, or nitro terminating group was achieved by use of a PdCl 2(Ph3P)2-Cs2CO3 reaction system to form a variety of carbocyclic compounds. Arylation in ketone compounds afforded benzene-annulated bridged or spirocycloalkanone derivatives, depending on the structure of the cyclization precursors. Arylation in formyl compounds occurred at the α-position (α-arylation) or at the carbonyl carbon (carbonyl-arylation) depending on the structure of the cyclization precursors and on the reaction solvent. An α-arylated secondary nitro group was partially transformed to ketone in the manner of the Nef reaction, whereas a tertiary nitro group was partially eliminated to afford a styrene-type olefin. Graphical Abstract
- Muratake, Hideaki,Natsume, Mitsutaka,Nakai, Hiroshi
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p. 11783 - 11803
(2007/10/03)
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- β-elimination of a phosphonate group from an alkoxy radical: An intramolecular acylation approach using an acylphosphonate as a carbonyl group acceptor
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On the basis of facile β-elimination of a phosphonate group from an alkoxy radical, intramolecular acylation reaction has been developed, in which an acylphosphonate is used as an excellent carbonyl group radical acceptor. Copyright
- Kim, Sunggak,Cho, Chang Ho,Lim, Chae Jo
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p. 9574 - 9575
(2007/10/03)
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- Baeyer-Villiger oxidations catalyzed by engineered microorganisms: Enantioselective synthesis of δ-valerolactones with functionalized chains
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Cyclohexanone monooxygenase (CHMO) from Acinetobacter sp NCIMB 9871 expressed in baker's yeast and in E. coli and cyclopentanone monooxygenase (CPMO) from Comamonas (previously Pseudomonas) sp. NCIMB 9872 expressed in E. coli are new bioreagents for Baeye
- Wang, Shaozhao,Chen, Gang,Kayser, Margaret M.,Iwaki, Hiroaki,Lau, Peter C.K.,Hasegawa, Yoshie
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p. 613 - 621
(2007/10/03)
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- Strictly regiocontrolled α-monosubstitution of cyclic carbonyl compounds with alkynyl and alkyl groups via Pd-catalyzed coupling of cyclic α-iodoenones with organozincs
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The conditions for the Pd-catalyzed cross coupling of cyclic α-iodoenones, such as 2-iodo-2-cyclohexenone, with alkynylzincs have been optimized. The use of tris(o-furyl)phosphine (TFP) as a ligand and DMF as a solvent has led to the formation of α-alkynylenones in excellent yields. This optimized procedure has been applied to the synthesis of (±)-harveynone and (±)-tricholomenyn A in high yields. Investigation of related α-alkylation reactions using alkylzincs has revealed the following. Methylzinc and primary alkylzinc derivatives readily undergo Pd-catalyzed cross coupling with α-iodoenones. Although (s-Bu)2Zn also undergoes Pd-catalyzed cross coupling, only the n-Bu-substituted products were obtained, α-Benzylation and α-homobenzylation can proceed satisfactorily, whereas allylzinc and propargylzinc derivatives undergo only addition to the carbonyl group. Although some promising results have been obtained in α-homoallylation and α-homopropargylation, these reactions need to be further improved. (C) 2000 Elsevier Science Ltd.
- Negishi, Ei-Ichi,Tan, Ze,Liou, Show-Yee,Liao, Baiqiao
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p. 10197 - 10207
(2007/10/03)
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- Palladium-catalyzed intramolecular α-arylation of aliphatic ketones
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Cyclization reaction of 5 - 10 using 10 mol% of PdCl2(Ph3P)2 in the presence of 3 eq. of Cs2CO3 in hot THF or toluene afforded bridged or spiro compounds 11 - 16 in good to moderate yields.
- Muratake, Hideaki,Natsume, Mitsutaka
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p. 7581 - 7582
(2007/10/03)
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- Consecutive 6-endo trigonal cyclisations from polyene acyl radical intermediates leading to decalone and perhydrophenanthrone ring constructions
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A range of substituted Se-phenyl 5,9-dieneselenoates, viz. 15a, 25, 26, 27, 42 and 52, have been synthesised and their reactions with Bu3SnH-AIBN investigated.The diene esters 15a, 42 and 52 are shown to lead to decalone and to perhydrophenanthrone derivatives, viz. 19, 43 and 53, respectively, via consecutive 6-endo trig modes of cyclisations starting from the corresponding 5,9-diene acyl radical intermediates.By contrast, the 5,9-dienoates 25 and 27 lacking alkyl substitution at C-9 instead underwent cyclisation to the indanones 36 and 37, respectively, and the 6-methyl substituted analogue 26 produced only the cyclopentanone 38 on treatment with Bu3SnH-AIBN.
- Chen, Ligong,Gill, G. Bryon,Pattenden, Gerald,Simonian, Houri
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- Baker's yeast reduction of arylidenecycloalkanones
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The baker's yeast reduction of arylidene cycloalkanones 5, 6 and 7 occurs initially through the catalysis of different enzymes to give the saturation of the double bond leading to the saturated ketones 9, 15 and 22 and the carbonyl reduction to the (S) allylic alcohols 8a, 14 and 23, possessing 0.99, 0.85 and 0.66 ee, respectively. The latter act as inhibitors for the carbonyl reducing enzyme thus preventing the further reduction of the saturated ketone. These compounds in the absence of allylic alcohols are further reduced to a mixture of diastereomic saturated (S) alcohols of high-moderate enantiomeric purity. Reduction experiments in D2O indicate that saturation of the double bond of 5 occurs by β re face addition of hydrogen, as shown by the obtainment of 10'.
- Fogliato, Giovanni,Fronza, Giovanni,Fuganti, Claudio,Lanati, Simonetta,Rallo, Roberta,Rigoni, Romina,Servi, Stefano
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p. 10231 - 10240
(2007/10/02)
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- Regioselective Aryl Radical Cyclization. 1. Stereocontrolled Synthesis of Linearly Condensed Hydroaromatic Carbocyclic Systems through 6-endo-ring Closures
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The stereocontrolled synthesis of trans-octahydroanthracenes 3, 11a-c, and 14a-c and trans-octahydro-5aH-cycloheptanaphthalene (27) through implementation of an efficient and highly regioselective 6-endo-trig-aryl radical cyclization of the respective 2-(o-bromoaryl)-1-methylenecyclohexanes 2, 10a-c, and 13a-c and 2-(o-bromobenzyl)-1-methylenecycloheptane (41) with tri-n-butyltin hydride id described.The radical cyclization of 2-(o-bromobenzyl)-1-methylenecyclopentane (43), in contrast, produced a mixture of the cis- and trans-hexahydro-1H-benzindenes (38) and (37).
- Pal, Sitaram,Mukhopadhyaya, Jayanta K.,Ghatak, Usha Ranjan
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p. 2687 - 2694
(2007/10/02)
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- Free-radical-mediated Carbonylative Cyclization of Alk-4-enyl Halides Leading to Cyclopentanone
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Alk-4-enyl bromides and iodides 1, when treated with the tributyltin hydride/CO sustem, undergo carbonylative cyclization to give cyclopentanones in good yields (AIBN cat., benzene, 79-90 atm, = 0.025-0.05 mol dm-3, 80 deg C.
- Ryu, Ilhyong,Kusano, Kazuya,Hasegawa, Mitsuharu,Kambe, Nobuaki,Sonoda, Noboru
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p. 1018 - 1019
(2007/10/02)
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- Effect of Fluoro Substitution on the Packing Motifs of Benzylidene- and Dibenzylidene-cyclopentanones
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The structure and solid-state reactivity of one fluorinated benzyl(benzylidene)cyclopentanone and two fluorinated dibenzylidenecyclopentanones are reported and the influence of fluoro substitution upon the packing of benzylidenecyclopentanones is discusse
- Hopkin, Sian E.,Muir, Maxwell,Theocharis, Charis R.
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p. 1131 - 1135
(2007/10/02)
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- TETRABUTYLAMMONIUM DIFLUOROTRIPHENYLSTANNATE AS A NEW ANHYDROUS SYNTHETIC EQUIVALENT TO TBAF
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Tetrabutylammonium difluorotriphenylstannate (1) is the first hypervalent complex of tin acting as a fluorinating agent.In contrast to TBAF and TASF, this crystalline complex is relatively stable up to 210 deg C and is not hygroscopic or hydrated.Enolsilylether alkylations with alkyl bromides proceeded in good to quantitative yields in the presence of (1), which was kept for years unprotected from moisture.Relative rate studies indicated that nucleophilic fluorination of benzyl bromide proceeded 18 times faster than with dried cesium fluoride in refluxing CH3CN.
- Gingras, Marc
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p. 7381 - 7384
(2007/10/02)
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- Desulfurization / α-Alkylation of β-Keto Sulfones
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A one-pot procedure for the reductive alkylation of β-keto sulfones is described.The method proceeds by a lithium in liquid ammonia desulfurization of the starting β-keto sulfone, resulting in regiospecific generation of an intermediate enolate.Subsequent
- Kurth, Mark, J.,O'Brien, Michael, J.
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p. 3846 - 3848
(2007/10/02)
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- A Cyclopentanone Annulation via Intramolecular Acylation of Alkylsilanes
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A facile construction of cyclopentanones is achieved via ring closure of 5-(trimethylsilyl)alkanoyl chlorides under the influence of AlCl3.
- Urabe, Hirokazu,Kuwajima, Isao
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p. 1140 - 1141
(2007/10/02)
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- Tris(dialkylamino)sulfonium Enolates. Synthesis, Structure, and Reactions
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A mixture of an enol trimethylsilyl ether and a fluoride salt exists in a dynamic equilibrium with an enolate species and fluorotrimethylsilane.Evacuation of an equimolar mixture of an enol trimethylsilyl ether of benzyl methyl ketone and tris(diethylamino)sulfonium (TAS) difluorotrimethylsiliconate produces fluorotrimethylsilane as the volatile fraction and the corresponding TAS enolate as air-sensitive crystals.The conductivity measurement and the 1H and 13C NMR analysis have substantiated the ionic nature of the TAS enolate in THF.The NMR chemical shifts are interpreted in terms of the electron distribution.The isolated TAS enolate undergoes O-acetylation with acetic anhydride and C-alkylation with methyl iodide exclusively.TAS enolate intermediates generated in situ from a series of enol silyl ethers and TAS difluorotrimethylsiliconate react with various active organic halides under mild conditions to give the regiospecific C-alkylation products.The in situ formed enolates react with aldehyde substrates to afford the β-trimethylsiloxy ketone adducts.In most cases, the reaction is kinetically controlled and the major products have erythro stereochemistry regardless of enolate configuration.This aldol reaction is postulated to proceed via an acyclic, extended transition state, in contrast to ordinary aldol reactions of Lewis acid coordinated enolates, which take place by way of six-membered chelate transition states.
- Noyori, R.,Nishida, I.,Sakata, J.
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p. 1598 - 1608
(2007/10/02)
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- Fluoride-Mediated Reactions of Enol Silyl Ethers. Regiospecific Monoalkylation of Ketones
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Treatment of enol silyl ethers with alkyl halides in the presence of benzyltrimethylammonium fluoride and molecular sieves at room temperature gives the corresponding monoalkylated products with high regiospecificity.In most cases no polyalkylated products formed in the reaction.The alkylation reaction is highly chemospecific: esters, epoxides, and even ketones survive the reaction conditions.The reactions of various cyclohexanone derivatives proceed with the preferential axial attack of the electrophile.
- Kuwajima, Isao,Nakamura, Eiichi,Shimizu, Makoto
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p. 1025 - 1030
(2007/10/02)
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- Alkylation via tris(dialkylamino)sulfonium enolates
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Tris(dialkylamino)sulfonium enolates generated from tris(diethylamino)sulfonium difluorotrimethylsiliconate and enol silyl ethers are readily alkylated by various alkyl halides under mild conditions.
- Noyori,Nishida,Sakata
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p. 2085 - 2088
(2007/10/02)
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