- Oxazolium Iodide Modified Perovskites for Solar Cell Fabrication
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Perovskites solar cells are gaining interest due to their attractive solar-to-electricity conversion efficiencies; however, they suffer from certain problems, such as suboptimal ion migration and stability issues. We report here on the inclusion of a phenyloxazolium salt (2-phenyl-3-methyloxazolium iodide) in perovskite solar cells based on methyl ammonium lead triiodide (MAPbI3). The fabricated solar cells not only displayed improved photovoltaic properties, but importantly the oxazolium cations can protect the perovskite layers from UV exposure as they down-convert electromagnetic irradiation; that is, the photons in the UV are absorbed and re-emitted at a different wavelength. The loading of 2-phenyl-3-methyloxazolium iodide in the perovskite precursor solution was optimized, the resulting perovskite films characterized, and the solar cells fabricated from them evaluated for their performance. Overall, this simple approach serves to optimize the performance parameters of perovskites films for solar cell applications.
- Salado, Manuel,Shirzadi, Erfan,Kazim, Samrana,Fei, Zhaofu,Nazeeruddin, Mohammad Khaja,Dyson, Paul J.,Ahmad, Shahzada
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Read Online
- Anodic methoxylation and acetoxylation of imines and imidates
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Anodic oxidation of cyclic imidates, 2-aryl-2-oxazolines, in methanol provided the corresponding 4-methoxylated products. Anodic α-methoxylation and α-acetoxylation of open-chain imines derived from glycine esters and benzophenone were also achieved using a bromide ion mediator. On the other hand, anodic α-acetoxylation of CF3-containing imine and imidate was successful without use of the bromine mediator. This is the first example of successful anodic α-substitution of imines and imidates.
- Baba, Daisuke,Fuchigami, Toshio
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Read Online
- Widely Exploited, Yet Unreported: Regiocontrolled Synthesis and the Suzuki–Miyaura Reactions of Bromooxazole Building Blocks
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An approach to synthesis of 2-, 4-, and 5-bromooxazoles is described. The method was optimized, and its scope was extended to all three isomeric parents, as well as various alkyl- and aryl-substituted bromooxazoles. It was found that direct regiocontrolled lithiation followed by reaction with electrophilic bromine source was common for all substrates and led exclusively to the target substituted 2-, 4- and 5-bromooxazoles on multigram scale. The utility of the multipurpose building blocks obtained in this work was demonstrated in the Suzuki–Miyaura cross-coupling reaction under parallel synthesis conditions.
- Solomin, Vitalii V.,Radchenko, Dmytro S.,Slobodyanyuk, Evgeniy Y.,Geraschenko, Oleksandr V.,Vashchenko, Bohdan V.,Grygorenko, Oleksandr O.
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p. 2884 - 2898
(2019/03/07)
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- Warming Up to Oxazole: Noncryogenic Oxazole Metalation and Negishi Coupling Development
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This report details the development of several suitable noncryogenic metalation conditions for the synthesis of oxazole zincate. Subsequent rounds of high-throughput catalyst screening ultimately led to the identification of several suitable Pd sources th
- Calimsiz, Selcuk,Geier, Michael J.,Humphreys, Luke D.,Scott, Mark E.,Wang, Xiaotian
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p. 1776 - 1781
(2019/09/09)
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- Reaction Conditions for the Regiodivergent Direct Arylations at C2- or C5-Positions of Oxazoles using Phosphine-Free Palladium Catalysts
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Two sets of reaction conditions for the regiodivergent C2- or C5- direct arylations of oxazole are reported. In both cases, phosphine-free catalysts and inexpensive bases were employed allowing the access to the arylated oxazoles in moderate to high yields. Using Pd(OAc)2/KOAc as catalyst and base, regioselective C5-arylations were observed; whereas, using Pd(acac)2/Cs2CO3 system, the arylation occurred at the C2-position of oxazole. The higher reactivity of C5-H bond of oxazole as compared to the C2-H bond in the presence of Pd(OAc)2/KOAc system is consistent with a concerted metalation deprotonation mechanism; whereas the C2-arylation likely occurs via a simple base deprotonation of the oxazole C2-position. Then, from these C2- or C5-arylated oxazoles, a second palladium-catalyzed direct C?H bond arylation affords 2,5-diaryloxazoles with two different aryl groups. We also applied these sequential arylations to the straightforward synthesis of 2-arylphenanthro[9,10-d]oxazoles via three C?H bond functionalization steps. The Ru-catalyzed C?H arylation of the aryl unit of 2-aryloxazoles is also described. (Figure presented.).
- Shi, Xinzhe,Soulé, Jean-Fran?ois,Doucet, Henri
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p. 4748 - 4760
(2019/09/12)
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- Versatile Photochemical Reactivity of Diverse Substituted 2-, 4- and 5-(o-Vinylstyryl)oxazoles
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To study the effects of the position of the hexatrienyl moiety on the oxazole ring, novel substituted cis/trans-2/4/5-(2-vinylstyryl)oxazoles have been synthesized. These novel compounds were prepared by Wittig reaction from the diphosphonium salt of α,α′-o-xylenedibromide, formaldehyde and the corresponding 2-methyl-4-, 4-methyl-2-, 2-pheny-5- and 4-methyl-5-oxazolecarbaldehyde, respectively. Aldehydes were synthesized by using several synthetic approaches. By applying intramolecular photocycloaddition, 2-methyl-4-(2-vinylstyryl)oxazole afforded, as major product, fused oxazoline-benzobicyclo[3.2.1]octene with small quantities of 4-(1,2-dihydronaphthalen-2-yl)-2-methyloxazole, as electrocyclization product. Upon irradiation of 4-methyl-5-(2-vinylstyryl)oxazole, endo- and exo-benzobicyclo[2.1.1]hexene products were formed by [2+2] cycloaddition; this was the first instance of the 1,4-closure to the bicyclo[2.1.1]hexene skeleton in the 2-, 4-, and 5-oxazole-stilbene derivatives studied so far. Derivatives 2-phenyl-5- and 4-methyl-2-(2-vinylstyryl)oxazole did not react and gave only high-weight molecular products but were crucial as a comparison in the overall mechanistic study. We have found that, depending on the position of the hexatrienyl moiety in the oxazole ring, as well as on the position of the methyl/phenyl substituents, these new vinylstyryl-2/4/5-oxazole derivatives show diverse photochemical behavior.
- ?agud, Ivana,?indler-Kulyk, Marija,Vojnovi?-Jandri?, Dragana,Marini?, ?eljko
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p. 515 - 524
(2018/02/09)
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- Arylation, Vinylation, and Alkynylation of Electron-Deficient (Hetero)arenes Using Iodonium Salts
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Arylation, vinylation, and alkynylation of electron-deficient arenes and heteroarenes have been achieved by chemoselective C-H zincation followed by copper-catalyzed coupling reactions using iodonium salts. This approach offers a direct and general access to a wide scope of (hetero)biaryls as well as alkenylated and alkynylated heteroarenes under mild conditions. It is particularly useful and valuable for the rapid and modular synthesis of diverse (hetero)aryl compounds, as demonstrated in the synthesis of transient receptor potential vanilloid 1 (TRPV1) antagonists and angiotensin II receptor type 1 (AT1 receptor) antagonists.
- Liu, Chuan,Wang, Qiu
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supporting information
p. 5118 - 5121
(2016/10/14)
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- C-H arylation and alkenylation of imidazoles by nickel catalysis: Solvent-accelerated imidazole C-H activation
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The first nickel-catalyzed C-H arylations and alkenylations of imidazoles with phenol and enol derivatives are described. Under the influence of Ni(OTf)2/dcype/K3PO4 (dcype: 1,2-bis(dicyclohexylphosphino)ethane) in t-amyl alcohol, imidazoles can undergo C-H arylation with phenol derivatives. The C-H arylation of imidazoles with chloroarenes as well as that of thiazoles and oxazoles with phenol derivatives can also be achieved with this catalytic system. By changing the ligand to dcypt (3,4-bis(dicyclohexylphosphino)thiophene), enol derivatives could also be employed as coupling partners achieving the C-H alkenylation of imidazoles as well as thiazoles and oxazoles. Thus, a range of C2-arylated and alkenylated azoles can be synthesized using this newly developed nickel-based catalytic system. The key to the success of the C-H coupling of imidazoles is the use of a tertiary alcohol as solvent. This also allows the use of an air-stable nickel(ii) salt as the catalyst precursor.
- Muto, Kei,Hatakeyama, Taito,Yamaguchi, Junichiro,Itami, Kenichiro
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p. 6792 - 6798
(2015/11/24)
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- One-pot conversion of amino acids into 2,5-disubstituted oxazoles: No metals needed
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2,5-Disubstituted oxazoles with a variety of alkyl and aryl groups are efficiently formed from N-acylamino acids, by a one-pot radical decarboxylation- oxidation-enolization and iodine-promoted cyclization process. Remarkably, the reaction takes place under mild conditions, and no metal catalysis is needed. The process can be useful for the direct modification of small peptides.
- Romero-Estudillo, Ivan,Batchu, Venkateswara Rao,Boto, Alicia
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supporting information
p. 3742 - 3748
(2015/01/16)
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- DDQ-induced dehydrogenation of heterocycles for c-c double bond formation: Synthesis of 2-thiazoles and 2-oxazoles
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Strong as an Ox: 2-Thiazoles and 2-oxazoles are formed by oxidation of 2-thiazolines and 2-oxazolines without requiring substituents at the C4 and C5 positions. DDQ plays an important role as the oxidant in this transformation and metal is unnecessary. This general procedure shows good functional group tolerance and provides a wide variety of 2-thiazoles and 2-oxazoles in moderate to excellent yields.
- Li, Xiangnan,Li, Cheng,Yin, Bing,Li, Cong,Liu, Ping,Li, Jianli,Shi, Zhen
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p. 1408 - 1411
(2013/07/26)
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- Nickel-catalyzed C-H arylation of azoles with haloarenes: Scope, mechanism, and applications to the synthesis of bioactive molecules
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Novel nickel-based catalytic systems for the C-H arylation of azoles with haloarenes and aryl triflates have been developed. We have established that Ni(OAc)2/bipy/LiOtBu serves as a general catalytic system for the coupling with aryl bromides and iodides as aryl electrophiles. For couplings with more challenging electrophiles, such as aryl chlorides and triflates, the Ni(OAc)2/dppf (dppf=1,1′-bis(diphenylphosphino)ferrocene) system was found to be effective. Thiazoles, benzothiazoles, oxazoles, benzoxazoles, and benzimidazoles can be used as the heteroarene coupling partner. Upon further investigation, we discovered a new protocol for the present coupling using Mg(OtBu)2 as a milder and less expensive alternative to LiOtBu. Attempts to reveal the mechanism of this nickel-catalyzed heterobiaryl coupling are also described. This newly developed methodology has been successfully applied to the syntheses of febuxostat (a xanthine oxidase inhibitor that is effective for the treatment of gout and hyperuricemia), tafamidis (effective for the treatment of TTR amyloid polyneuropathy), and texaline (a natural product having antitubercular activity). Copyright
- Yamamoto, Takuya,Muto, Kei,Komiyama, Masato,Canivet, Jerome,Yamaguchi, Junichiro,Itami, Kenichiro
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experimental part
p. 10113 - 10122
(2011/10/08)
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- HETEROARYL COMPOUNDS AND METHODS OF USE THEREOF
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Provided herein are heteroaryl compounds, methods of their synthesis, pharmaceutical compositions comprising the compounds, and methods of their use. In one embodiment, the compounds provided herein are useful for the treatment, prevention, and/or management of various disorders, such as CNS disorders and metabolic disorders, including, but not limited to, e.g., neurological disorders, psychosis, schizophrenia, obesity, and diabetes
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Page/Page column 106-107
(2011/12/14)
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- A powerful palladium-catalyzed multicomponent process for the preparation of oxazolines and benzoxazoles
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Efficient and convenient three-component couplings of an aryl halide, isocyanide, and an amino alcohol under palladium catalysis provide a range of oxazolines and benzoxazoles in excellent yield.
- Boissarie, Patrick J.,Hamilton, Zoe E.,Lang, Stuart,Murphy, John A.,Suckling, Colin J.
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scheme or table
p. 6256 - 6259
(2012/01/06)
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- Modulating reactivity and diverting selectivity in palladium-catalyzed heteroaromatic direct arylation through the use of a chloride activating/blocking group
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(Chemical Equation Presented) Through the introduction of an aryl chloride substituent, the selectivity of palladium-catalyzed direct arylation may be diverted to provide alternative regioisomeric products in high yields. In cases where low reactivity is typically observed, the presence of the carbon-chlorine bond can serve to enhance reactivity and provide superior outcomes. From a strategic perspective, the C-Cl bond is easily introduced and can be employed in a variety of subsequent transformations to provide a wealth of highly functionalized heterocycles with minimal substrate preactivation. The impact of the C-Cl functional group on direct arylation reactivity has also been evaluated mechanistically, and the observed reactivity profiles correlate very well with that predicted by a concerted metalation-deprotonation pathway.
- Liegault, Benoit,Petrov, Ivan,Gorelsky, Serge I.,Fagnou, Keith
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supporting information; experimental part
p. 1047 - 1060
(2010/04/04)
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- Highly regioselective palladium-catalyzed direct arylation of oxazole at C-2 or C-5 with aryl bromides, chlorides, and triflates
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Complementary palladium-catalyzed methods for direct arylation of oxazole with high regioselectivity (>100:1) at both C-5 and C-2 have been developed for a wide range of aryl and heteroaryl bromides, chlorides, iodides, and triflates. C-5 arylation is pre
- Strotman, Neil A.,Chobanian, Harry R.,Guo, Yan,He, Jiafang,Wilson, Jonathan E.
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supporting information; experimental part
p. 3578 - 3581
(2010/11/04)
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- 2,3-dichloro-5,6-dicyano-1,4-benzoquinone-catalyzed teactions employing MnO2 as a stoichiometric oxidant
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Several oxidative reactions can be effected with MnO2 in the presence of substoichiometric quantities of DDQ. These transformations include oxidative cyclization, deprotection, and dehydrogenation reactions. The use of MnO2 as a terminal oxidant for DDQ-mediated reactions is attractive based on economical and environmental factors.
- Liu, Lei,Floreancig, Paul E.
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supporting information; experimental part
p. 4686 - 4689
(2010/12/24)
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- An effective C-C double bond formation via Cu(I)-catalyzed dehydrogenation
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A dehydrogenation method using Cu(I) and either N,N-di-tert-butylthiadiaziridine 1,1-dioxide or N,N-di-tert-butyldiaziridinone is reported. The dehydrogenation allows a facile introduction of C-C double bond(s) into various carbocycles and heterocycles such as oxazolines and thiazolines.
- Ramirez, Thomas A.,Zhao, Baoguo,Shi, Yian
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scheme or table
p. 1822 - 1825
(2010/09/07)
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- Nickel-catalyzed biaryl coupling of heteroarenes and aryl halides/triflates
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Ni-based catalytic systems for the arylation of heteroarenes with aryl halides and triflates have been established. Ni(OAc)2/bipy is a general catalyst for aryl bromides/iodides, and Ni(OAc)2/dppf is effective for aryl chlorides/triflates. Thiazole, benzothiazole, oxazole, benzoxazole, and benzimidazole are applicable as heteroarene coupling partners. A rapid synthesis of febuxostat, a drug for gout and hyperuricemia, is also demonstrated.
- Canivet, Jerome,Yamaguchi, Junichiro,Ban, Ikuya,Itami, Kenichiro
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supporting information; experimental part
p. 1733 - 1736
(2009/08/15)
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- Nickel-catalyzed synthesis of oxazoles via C-S activation
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The synthesis of 2-substituted oxazoles is achieved via nickel-catalyzed cross-coupling reaction of 2-methylthio-oxazole and various organozinc reagents. An extension of this method is demonstrated with a chemoselective, one-pot synthesis of unsymmetrical
- Lee, Kyoungsoo,Counceller, Carla M.,Stambuli, James P.
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supporting information; experimental part
p. 1457 - 1559
(2009/08/08)
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- COPPER-CATALYZED C-H BOND ARYLATION
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The present invention is a one-step method for efficiently converting carbon-hydrogen bonds into carbon-carbon bonds using a combination of aryl halides, a substrate, and a copper salt as catalyst. This method allows faster introduction of complex molecular entities, a process that would otherwise require many more steps. This invention is particularly relevant for the organic synthesis of complex molecules such as, but not limited to, pharmacophores and explosives.
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Page/Page column 16-17
(2009/04/24)
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- C-H bond activation: A versatile protocol for the direct arylation and alkenylation of oxazoles
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The versatile palladium, complex Pd(PPh3)4 catalyses both direct arylation and alkenylation of oxazoles efficiently. The method is regioselective and stereospecific with respect to bromoalkenes and tolerates a wide range of functional groups.
- Besselievre, Francois,Lebrequier, Sabrina,Mahuteau-Betzer, Florence,Piguel, Sandrine
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experimental part
p. 3511 - 3518
(2010/02/28)
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- Direct arylations on water: Synthesis of 2,5-disubstituted oxazoles balsoxin and texaline
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An efficient two-step palladium catalysed synthesis of 2,5-disubstituted oxazoles is reported. The Royal Society of Chemistry.
- Ohnmacht, Stephan A.,Mamone, Patrizia,Culshaw, Andrew J.,Greaney, Michael F.
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p. 1241 - 1243
(2008/12/21)
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- Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): an efficient catalyst for regioselective C-2 arylation of heterocycles
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Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate), a structurally well defined O-containing transition metal complex is reported as an efficient catalyst for regioselective direct C-2 arylation of heterocycles with aryl halides. The present protocol is applicable to a wide variety of heterocycles providing good to excellent yields of products.
- Nandurkar, Nitin S.,Bhanushali, Mayur J.,Bhor, Malhari D.,Bhanage, Bhalchandra M.
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p. 1045 - 1048
(2008/09/17)
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- A versatile synthesis of 2,4-substituted oxazoles
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A variety of five-membered ring oxazoles have been synthesised with complete regiocontrol and without the requirement for ring oxidation via a reaction sequence based on a vinyl sulfonamide template. The Royal Society of Chemistry.
- Chudasama, Vijay,Wilden, Jonathan D.
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supporting information; experimental part
p. 3768 - 3770
(2009/02/07)
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- Copper-catalyzed arylation of heterocycle C-H bonds
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A new method for the direct, copper-catalyzed arylation of heterocycle C-H bonds by aryl halides has been developed. In addition to electron-rich five-membered heterocycles, electron-poor pyridine oxides can also be arylated. The best results are obtained by using a combination of lithium tert-butoxide base, aryl iodide coupling partner, and copper iodide catalyst. Copyright
- Do, Hien-Quang,Daugulis, Olafs
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p. 12404 - 12405
(2008/09/17)
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- Deprotonation of benzoxazole and oxazole using lithium magnesates
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The first deprotonations of oxazole and benzoxazole using lithium magnesates are described. The reactions occurred in tetrahydrofuran at room temperature using 1/3 equiv of lithium tributylmagnesate. As 2-lithiooxazole and 2-lithiobenzoxazole, lithium tri(2-oxazolyl)magnesate and lithium tri(2-benzoxazolyl)magnesate very rapidly and completely isomerized to the more stable 2-(isocyano)enolate and 2-(isocyano)phenolate type structures, respectively, a result shown by NMR analysis. The isolation of 2-substituted oxazoles and benzoxazoles in medium to good yields after electrophilic trapping was interpreted in two ways: (1) the equilibration between the open and closed structures is faster than the trapping of the open isomers, and the closed isomers are more reactive than the open ones, or (2) the open isomers react with electrophiles in a intramolecular Passerini type reaction. The nonreactivity of the 2-(isocyano)enolate type structure toward anisaldehyde in the absence of lithium bromide makes the intramolecular Passerini type reaction more plausible.
- Bayh, Omar,Awad, Hacan,Mongin, Florence,Hoarau, Christophe,Bischoff, Laurent,Trecourt, Francois,Queguiner, Guy,Marsais, Francis,Blanco, Fernando,Abarca, Belen,Ballesteros, Rafael
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p. 5190 - 5196
(2007/10/03)
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- Stereoselective electrogeneration of (E)-4-alkoxy-2-phenyl-5-chloro-2- oxazolines by cathodic reduction of N-(1-alkoxy-2,2,2-trichloroethyl)benzamides
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The first method for the synthesis of the title compounds has been established. Quantitative reactions of benzamides with chloral hydrate provided chloralbenzamides which were efficiently converted to N-(1,2,2,2- tetrachloroethyl)amides by treatment with
- Guirado, Antonio,Andreu, Raquel,Martiz, Bruno,Gálvez, Jesús
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p. 987 - 991
(2007/10/03)
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- Cobalt-catalyzed arylation of azole heteroarenes via direct C-H bond functionalization
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(Equation presented) We herein report a new cobalt-catalyzed method for arylation of azole heteroarenes, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole. The direct arylation of thiazole and oxazole was achieved both with iodo- and bromoarenes as the aryl donors in the presence of cobalt catalyst [Co(OAc)2/IMes] and cesium carbonate, while imidazole required the use of zinc oxide as the base. A complete reversal of arylation from C-5 to C-2 was accomplished using the bimetallic Co/Cu/IMes system. A direct comparison of the new cobalt method and the previously developed palladium protocol revealed significant differences, in terms of both chemical yield and selectivity.
- Sezen, Bengue,Sames, Dalibor
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p. 3607 - 3610
(2007/10/03)
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- A practical approach to the synthesis of 2,4-disubstituted oxazoles from amino acids
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(Matrix presented) A new sequence for the synthesis of various 2,4-disubstituted oxazoles from α-amino acids is reported. The method is shown to be general and incorporates the reagent combination, triphenylphosphine/hexachloroethane, for cyclodehydration of intermediate α-acylamino aldehydes. Implementation of this reagent system for the conversion of α-acylamino ketones to oxazoles is briefly investigated.
- Morwick, Tina,Hrapchak, Matt,DeTuri, Molly,Campbell, Scot
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p. 2665 - 2668
(2007/10/03)
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- Pummerer reaction methodology for the synthesis of 5-thiophenyl substituted oxazoles
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Treatment of N-acylamino-2-thiophenyl derivatives with N-chlorosuccinimide (2.0 equiv.) followed by SnCl4 (0.1-1.0 equiv.) provides a direct synthesis of 5-thiophenyloxazoles.
- Kreisberg, Jennifer D,Magnus, Philip,Shinde, Shirin
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p. 7393 - 7396
(2007/10/03)
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- Oxazole derivatives, process for producing the same, and herbicide
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The present invention is directed to oxazole derivatives represented by the formula ?I!; STR1 wherein A represents a nitrogen atom or a R3 -substituted carbon atom; B represents a nitrogen atom, or an unsubstituted or X-substituted carbon atom; Z represents an oxygen atom, sulfinyl or sulfonyl; R1 and R2 represent each independently hydrogen, C1 -C6 alkyl, C1 -C6 alkoxy, C1 -C6 haloalkoxy, C1 -C6 haloalkyl or the like; R3 represents hydrogen, C1 -C6 alkyl, halogen, nitro, formyl or acyl; X represents hydrogen, C1 -C6 alkyl, C3 -C7 cycloalkyl, C2 -C6 alkenyl, C3 -C6 alkynyl, C1 -C6 haloalkyl or the like; Y represents hydrogen, C1 -C6 alkyl, C3 -C7 cycloalkyl, C2 -C6 alkenyl, C3 -C6 alkynyl, C1 -C6 haloalkyl or the like; m represents an integar of 1 or 2, and n represents an integar of 1, 2, 3 or 4, and the salts thereof. The compounds specified in the present invention have an excellent herbicidal activity and are useful as an active ingredients for herbicides.
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- Chemistry of 5-oxodihydroisoxazoles. Part 18. Synthesis of oxazoles by the photolysis and pyrolysis of 2-acyl-5-oxo-2,5-dihydroisoxazoles
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N-Acylisoxazol-5-ones lose carbon dioxide under photochemical and thermal conditions affording iminocarbenes which undergo intramolecular cyclisation through the oxygen of the acyl group to give oxazoles. Under photochemical conditions those acylisoxazolones with electron withdrawing groups at C-4 usually give high yields of oxazoles, while those with electron donating groups at C-4 give only poor yields: the reverse is observed under thermal conditions.
- Prager, Rolf H.,Smith, Jason A.,Weber, Ben,Williams, Craig M.
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p. 2665 - 2672
(2007/10/03)
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- The synthesis of oxazoles by thermolysis or photolysis of 2-acylisoxazol-5-ones
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N-acylisoxazol-5-ones are converted into the corresponding 2-substituted oxazoles by photolysis at 300 or 254 nm, or by flash vacuum pyrolysis. The former procedure is favoured for isoxazolones with electron withdrawing groups at C-4, and pyrolysis for all others.
- Ang, Kiah H.,Prager, Rolf H.,Smith, Jason A.,Weber, Ben,Williams, Craig M.
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p. 675 - 678
(2007/10/02)
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- 2-Metallated Oxazoles; pKa Dependent Deuterations, NMR Studies and Palladium Catalysed Couplings
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Deuteration experiments on 2-lithiated oxazoles show a pKa dependent regioselectivity suggesting that the ring cleaved tautomer dominates the equilibrium.Transmetallation to the zinc derivative gives a species which behaves as a C2 ring closed nucleophile as judged by deuteration and palladium catalysed coupling experiments.These conclusions are supported by nmr spectroscopy studies of the metallated species.
- Crowe, Eleanor,Hossner, Frank,Hughes, Mark J.
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p. 8889 - 8900
(2007/10/03)
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- A Retro-Diels-Alder Approach to Oxazoles and Imidazoles
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Heating N-acyl derivatives 4 of 3-endo-aminobicyclohept-5-en-2-endo-ol (3) at 185-195 deg C for 4-5 h provides oxazoles 1a-e in 49-88percent yields.The reaction proceeds via an initial dehydration to an oxazoline which undergoes retro-Diels-Alder reaction to provide the oxazole.Similarly, imidazoles 7a-f may be obtained in 40-79percent yields by heating imidazolines 6a-f to effect the cycloreversion.
- Eissenstat, Michael A.,Weaver, John D.
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p. 3387 - 3390
(2007/10/02)
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- A New Synthesis of Highly Functionalized Oxazoles
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Functionalized oxazoles and bis-oxazoles are obtained by side-chain oxidation of β-hydroxy amides with the Dess-Martin periodinane, followed by cyclodehydration with triphenylphosphine/iodine in the presence of triethylamine.
- Wipf, Peter,Miller, Chris P.
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p. 3604 - 3606
(2007/10/02)
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- SYNTHESE DE PYRROLES ET D'OXAZOLES PAR PYROLYSE DE N-(HYDROXY-2' ETHYL) AMINO-3 PROPENOATE
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The gas phas pyrolysis of various N-(2'-hydroxyethyl)-3-amino propenoates 1-6 and N-(2'-hydroxy-2'-phenyl ethyl)-3-amino propanoate 7-9 at 390 deg C-420 deg C leads respectively to formylpyrroles 11-16 and benzoylpyrroles 17-19 and, in some cases, to substituted oxazoles 36-39.The results are best explained by the intermediate formation of a dicarbonyl derivative followed either by an intramolecular thermal crotonisation or a six ? electrocyclization of an azomethine ylide.
- Pale-Grosdemange, Catherine,Chuche, Josselin
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p. 3397 - 3414
(2007/10/02)
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- Synthesis of 2-Aryl- and 5-Alkyl-2-aryloxazoles from 2-Aryl-5-bromooxazoles
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2-Aryloxazoles, their 5-deuterio derivatives, and 5-alkyl-2-aryloxazoles are prepared in good yields from 2-aryl-5-bromooxazoles via halogen/metal exchange with butyllithium followed by treatment with water, methanol-O-d, or alkyl halides, respectively.
- Kashima, Choji,Arao, Hideki
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p. 873 - 874
(2007/10/02)
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- SYNTHESIS OF 2-ARYL AND 2-HETARYLOXAZOLES FROM THE OXAZOLINES AND OXAZOLIDINES
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Treatment of 2-phenyl-, 2-(2-furyl)-, and 2-(2-thienyl)oxazolines with nickel peroxide has been found to give, in addition to the dehydrogenation products (2-substituted oxazoles),the fragmentation products (amides of benzoic, furan-2-carboxylic, and thiophen-2-carboxylic acids).This fragmentation appears to give initially the nitriles, which are then converted into the amides by the nickel peroxide.Catalytic dehydrogenation of 2-phenyloxazoline gives low yields of 2-phenyloxazole, the principal product being benzonitrile.Treatment of the Schiff's bases obtained from ethanolamine and aldehydes (benzaldehyde, furfural, and thiophen-2-aldehyde) with nickel peroxide gives trace amounts of the oxazoles, the principal products being the aldehydes, with smaller amounts of the nitriles.
- Belen'kii, L. I.,Cheskis, M. A.,Ryashentseva, M. A.
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p. 650 - 653
(2007/10/02)
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- SYNTHESIS AND SOME ELECTROPHILIC SUBSTITUTION REACTIONS OF 2-PHENYLOXAZOLE
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A new synthesis of 2-phenyloxazole that includes the preparation of 2-phenyloxazoline and aromatization of the latter by the action of nickel peroxide was developed.It was established that under conditions that exclude protonation electrophilic substituti
- Belen'kii, L. I.,Cheskis, M. A.
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p. 713 - 716
(2007/10/02)
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