- Styrylisoxazole-based fluorescent probes for the detection of hydrogen sulfide
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Styrylisoxazoles bearing a nitro group linked to bulky aromatic rings have been synthesized and examined for their absorption and emission studies in organic solvents and water. The molecules showed emission in the visible region with significant solvatochromic emission shifts influenced by the extended conjugation of aromatic rings and intramolecular charge transfer. These absorption and emission changes were used for the efficient and sensitive detection of trace concentrations of hydrogen sulfide (H2S) through the reduction of the nitro group to the amine group in the presence of aqueous sodium sulfide. The experimental results indicated that the probes exhibit an excellent emission response with large shifts in the emission and sensitivity with a micromolar detection limit.
- Katla, Jagadish,Kanvah, Sriram
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Read Online
- Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis
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The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2→ ArB(OH)2) and protodeboronation (ArB(OR)2→ ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F,1H, and11B), pH-rate dependence, isotope entrainment,2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKaof the boronic acid/ester.
- Hayes, Hannah L. D.,Wei, Ran,Assante, Michele,Geogheghan, Katherine J.,Jin, Na,Tomasi, Simone,Noonan, Gary,Leach, Andrew G.,Lloyd-Jones, Guy C.
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supporting information
p. 14814 - 14826
(2021/09/13)
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- Development of Gold-catalyzed [4+1] and [2+2+1]/[4+2] Annulations between Propiolate Derivatives and Isoxazoles
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Two new gold-catalyzed annulations of isoxazoles with propiolates have been developed. Most isoxazoles follow an initial O attack on the alkyne to afford a [4+1] annulation product. This process results in a remarkable alkyne cleavage of initial propiolates. Unsubstituted isoxazoles proceed through an N attack step to yield formal [2+2+1]/[4+2] annulation products. These two annulation products arise initially from two seven-membered heterocyclic intermediates, which then lead to products.
- Sahani, Rajkumar Lalji,Liu, Rai-Shung
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supporting information
p. 1026 - 1030
(2017/01/18)
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- Reductive ring opening of 3,5-bis(2-arylethenyl)isoxazoles with molybdenum hexacarbonyl: A novel route to symmetrical and unsymmetrical curcumin derivatives
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Curcumin derivatives were successfully synthesized from 3,5-dimethylisoxazole by lateral metalation and condensation with various aromatic aldehydes sequentially at C5- and C3-methyl groups. After dehydration, further transformation of isoxazole ring to β-diketone moiety was accomplished by reductive ring opening using molybdenum hexacarbonyl [Mo(CO)6] and subsequent simple acidic hydrolysis.
- Hahnvajanawong, Viwat,Thaima, Thanaphat,Tearavarich, Ruchanok,Theramongkol, Parinya
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p. 127 - 135
(2016/05/09)
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- Development and Scale-up of an Organocatalytic Enantioselective Process to Manufacture (S)-Pregabalin
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Herein is reported the development of a new process to manufacture (S)-pregabalin. The method comprises six steps, run under the catalysis of a recyclable polymer bound phase transfer catalyst, and afforded (S)-pregabalin in overall 54% yield, starting from building blocks acetylacetone, isovaleraldehyde, and nitromethane.
- Moccia, Maria,Cortigiani, Mauro,Monasterolo, Claudio,Torri, Federica,Del Fiandra, Claudia,Fuller, Geoffrey,Kelly, Brian,Adamo, Mauro F. A.
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p. 1274 - 1281
(2015/09/28)
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- Organocatalyzed asymmetric vinylogous Michael addition of α,β-unsaturated γ-butyrolactam
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Highly efficient asymmetric vinylogous 1,6-Michael addition of α,β-unsaturated γ-butyrolactam to 3-methyl-4-nitro-5-alkenyl- isoxazoles and Michael addition to trichloromethyl ketones by using a chiral quinine-derived squaramide organocatalyst were described, giving products with high diastereo- and enantioselectivities (up to >25:1 dr and 96% ee).
- Zhang, Jinlong,Liu, Xihong,Ma, Xiaojuan,Wang, Rui
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supporting information
p. 9329 - 9331
(2013/10/01)
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- Continuous-flow microliter microwave irradiation in the synthesis of isoxazole derivatives: An optimization procedure
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An efficient method was developed for the synthesis of 3,4,5-trisubstituted and 3,5-disubstituted isoxazoles by using continuous-flow microwave-heated microreactors. A study on the separate effects of the temperature, continuous-flow regime, and microwave irradiation showed that the continuous-flow regime had important effects for less reactive diketones, where microwave heating enhanced the reaction, permitting the formation of 5-methyl-3-phenylisoxazole, which was not formed in the absence of microwaves. Georg Thieme Verlag Stuttgart · New York.
- Rodriguez, Antoniom.,Juan, Alberto,Gomez, M.Victoria,Moreno, Andres,De La Hoz, Antonio
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experimental part
p. 2527 - 2530
(2012/08/29)
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- Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies
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The first photocycloadditions of aromatic and aliphatic aldehydes to methylated isoxazoles are reported. The reactions lead solely to the exo-adducts with high regio- and diastereoselectivities. Ring methylation of the isoxazole substrates is crucial for high conversions and product stability. The 6-arylated bicyclic oxetanes 9a-9c were characterized by X-ray structure analyses and showed the highest thermal stabilities. All oxetanes formed from isoxazoles were highly acid-sensitive and also thermally unstable. Cleavage to the original substrates is dominant and the isoxazole derived oxetanes show type T photochromism.
- Griesbeck, Axel G.,Franke, Marco,Neudoerfl, Joerg,Kotaka, Hidehiro
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experimental part
p. 127 - 134
(2011/05/16)
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- Heteropolyacids as green and reusable catalysts for the synthesis of isoxazole derivatives
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Heteropolyanions with different structures, including Keggin, Dawson, Preyssler, mixed addenda, and sandwich types, catalyzed the formation of 1,3-diphenyl-isoxazole from the condensation of 1,3-diphenyl-propane-1,3-dione and hydroxylamine hydrochloride in different solvents and under heating conditions. Our data vividly indicate that H3PW11CuO40 is the catalyst of choice and could catalyze the synthesis of other isoxazole derivatives in high yields and good selectivities. Copyright Taylor & Francis Group, LLC.
- Heravi, Majid M.,Derikvand, Fatemeh,Haeri, Anahita,Oskooie, Hossein A.,Bamoharram, Fatemeh F.
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p. 135 - 140
(2008/03/14)
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- Recyclization of Pyrimidin-2(1H)-one into 2-Isoxazoline and 2-Pyrazoline
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A reaction of 1-aryl-4,6-dimethylpyrimidin-2(1H)-ones with hydroxylamine and acetylhydra-zine leads to previously unknown 5-N-arylcarbamoylamino derivatives of 3,5-dimethyl-2-isoxazoline and 2-pyrazoline. The structure of the compounds obtained was confirmed by 1H and 13C NMR as well as independent synthesis by reacting phenyl isocyanate with 5-amino-3,5-dimethyl-2-isoxazoline and 1-acetyl-2-pyrazoline.
- Ershov,Gindin,Gribanov
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p. 388 - 391
(2007/10/03)
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- An efficient, scaleable procedure for the conversion of esters to isoxazoles
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A concise, regiocontrolled route to isoxazoles, based on the condensation of an ester with a metallated imine, has been developed. The intermediate vinylogous amides react smoothly with hydroxylamine to provide, after dehydration, substituted isoxazoles. The method has been used for the multi-kilo scale preparation of ABT-418, a novel cholinergic channel activator.
- Bunnelle,Singam,Narayanan,Bradshaw,Liou
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p. 439 - 442
(2007/10/03)
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- Lewis acid mediated addition of tri-n-butyl-stannylmethylisoxazole with aldehydes
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Lewis acid mediated addition of 5-(tri-n-butylstannyl)methyl-3-methylisoxazole and its analogues with aldehydes have been carried out. Corresponding 5-(β-hydroxy)ethylisoxazoles were obtained in moderate yields, without ring opening of the isoxazole.
- Yamamoto, Makoto,Ohtsuka, Kazumi,Kishikawa, Keiki,Kohmoto, Shigeo
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p. 2177 - 2187
(2007/10/03)
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- N-HYDROXYAMIDE-CONTAINING HETEROCYCLES. PART 3. THE RING TRANSFORMATION OF 1-BENZYLOXY-2(1H)-PYRIMIDINONES INTO 2-ISOXAZOLINES WITH HYDROXYLAMINE
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N-Benzyloxyurea was treated various β-diketones on the presence of sulfuric acid in EtOH to give the corresponding 1-benzyloxy-2(1H)-pyrimidinones. 1-Benzyloxy-2(1H)-pyrimidinonesunderwent the ring transformation with hydroxylamine to afford new 5-N-(benzyloxy)urea-attached 2-isoxazolines in addition to known isoxazoles.The MNDO molecular orbital calculation of 1-benzyloxy-4,6-dimethyl-2(1H)-pyrimidinone and the reaction mechanism are also discussed.
- Katoh, Akira,Ohkanda, Junko,Tamura, Atsushi,Yoshiike, Yuji,Mitsuhashi, Keiryo
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p. 1141 - 1146
(2007/10/02)
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- Di-heterocyclic compounds and their use as antiviral agents
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Compounds of the formulas: STR1 wherein Het is an oxazole or oxazine moiety; X is O, S or SO, n is an integer from 3 to 9, Y is an aliphatic bridge; and the various R groups represent hydrogen or various substituents as described herein, are useful as antiviral agents, especially against picornaviruses. N-(Chloroalkyl)amide intermediates for the compounds of Formula I are also active as antiviral agents. Related compounds outside the scope of the above formulas are also disclosed.
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- Preparation of N-Silyl-enamines from α-Silyl Carbanions and Aromatic Nitriles
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The preparations of seven N-silyl-enamines (1a) - (1g) and their chemical behaviour are reported.Lithiated 4-(trimethylsilylmethyl)pyridine (2b) easily reacted with benzonitrile (4a) in tetrahydrofuran to give only (E)-1-phenyl-2-(4-pyridyl)-1-(trimethylsilylamino)ethene (1b) in 90percent yield.On the other hand, lithiated t-butyl trimethylsilylacetate (2c) did not react with (4a) at all, but reacted readily with 2- or 4-cyanopyridines, (4b) or (4c), and scarcely at all reacted with 3-cyanopyridine (4d) to give the corresponding t-butyl (Z)-3-trimethylsilylamino-3-pyridylpropenoates (1c), (1d), and (1e) in 68, 75, and 4percent yields, respectively.The reaction of 3-methyl-5-(trimethylsilylmethyl)isoxazole (2d) with the nitriles (4a) or (4b) gave the corresponding N-silyl-enamine (1g) or the desilylated enamines (5b,c), which were unstable and were readily hydrolyzed to the corresponding ketones (6a) or (6b).
- Konakahara, Takeo,Kurosaki, Yoshihiro
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p. 1068 - 1086
(2007/10/02)
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- REACTIONS OF NITRILE OXIDES WITH PHENYLSULPHINYLPROPA-1,2-DIENE AND 1-PHENYLTHIOPROP-2-ENE. NEW ROUTES TO FUNCTIONALIZED α,β-UNSATURATED KETONE EQUIVALENTS
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Nitrile oxides add regiospecifically to the terminal double bonds in (1) and (3).The adducts (4a-e) were readily cleaved and converted into enone equivalents (8).
- Brown, Roger S.,Eyley, Stephen C.,Parsons, Philip J.
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p. 633 - 642
(2007/10/02)
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- Metal-carbonyl-Induced Reaction of Isoxazoles. Ring Cleavage and Reduction by Hexacarbonylmolybdenum, Pentacarbonyliron, or Nonacarbonyldi-iron
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In the presence of and water the isoxazoles (1a-f) undergo thermally induced reductive cleavage of the N-O bond to give β-amino enones in good yield.Similar results were obtained by the use of and water with photoirradiation, or of and water with heating.A mechanism involving an N-complexed isoxazolepentacarbonylmolybdenum or isoxazoletetracarbonyliron, and a - or -complexed (β-oxo vinyl)nitrene intermediate is proposed for the reactions.The complexed nitrene moiety could be reduced by the central metal in the presence of water to give amine.Furthermore, treatment of 2-benzoyl- 3-phenyl-2-H-azirine (8a), which is an isomer of 3,5-diphenylisoxazole, with the metal carbonyls and water also resulted in the formation of a β-amino enone possibly via the corresponding complexed (β-oxo vinyl)nitrene.An N-complexed isoxazole-pentacarbonylmolybdenum intermediate was prepared by the photoreaction of with 3,5-dimethylisoxazole.Its characterization, and chemical transformations, have been carried out to investigate the proposed mechanism.
- Nitta, Makoto,Kobayashi, Tomoshige
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p. 1401 - 1406
(2007/10/02)
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- RING TRANSFORMATION REACTION OF 1,4,6-TRISUBSTITUTED 2(1H)-PYRIMIDINONES AND -THIONES WITH HYDROXYLAMINE
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1,4,6-Trisubstituted 2(1H)-pyrimidinones (Ia-e) underwent ring transformation with hydroxylamine to afford 3,5-disubstituted isoxazoles (IIa-e) in high yields.On the other hand, 2(1H)-pyrimidinethiones (IIIa, b, f-k) underwent ring transformation to give mainly a new type of N-substituted 2-aminopyrimidine 1-oxides (IVa, b, f-k) as well as isoxazoles.The reaction of pyrimidinium salts (VII, VIII, and IX) with hydroxylamine is also discussed.Keywords: - ring tranformation reaction; hydroxylamine; nucleophilic reaction; 3,5-disubstituted isoxazoles; N-substituted 2-aminopyrimidine 1-oxides; pyrimidinium salts
- Kashima, Choji,Katoh, Akira,Yokota, Yuko,Omote, Yoshimori
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p. 2516 - 2519
(2007/10/02)
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- Gas-Phase Thermal Isomerization of Some Aminomethylisoxazoles
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The kinetic results from the gas-phase thermal isomerization of 5-amino-3,4-dimethylisoxazole (1), 3,5-dimethylisoxazole (2), and 3-amino-5-methylisoxazole (3) are reported.Compound 1 afforded quantitatively 3-carbamoyl-2,3-dimethyl-1-azirine (4).On the other hand, 2 and 3 gave the isomeric oxazoles 5 and 7, respectively.Different reaction pathways are discussed according to the activation parameters.
- Perez, Jorge D.,Diaz, Rosario G. de,Yranzo, Gloria I.
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p. 3505 - 3508
(2007/10/02)
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- Halogenation of N-Oxygenated Pyrazoles. Preparation of N-Oxygenated 4-Halopyrazole and 4,4-Dihalo-4H-pyrazole Derivatives
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Reaction of some 1-hydroxypyrazoles and 1-hydroxypyrazole 2-oxides with iodine or with 1 equiv of N-chloro- or N-bromosuccinamide (NCS or NBS) gives high yields of the 4-halo derivatives.With 2 equiv of NBS or NCS or with tert-butyl hypochlorite the products are 4,4-dihalo-4H-pyrazole 1-oxides or 1,2-dioxides.Reaction of 3,5-diphenylpyrazole with 2 equiv of tert-butyl hypochlorite gives 1,4-dichloro-3,5-diphenylpyrazole, which rearranges to 4,4-dichloro-3,5-diphenyl-4H-pyrazole.Silver ion assisted solvolysis of the gem-dihalides to form 4-chloro-3H-pyrazole derivatives is described.
- Hansen, John F.,Kim, Yong In,Griswold, Linus J.,Hoelle, Gary W.,Taylor, Deborah L.,Vietti, David E.
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- GROUP IVB ORGANOMETALLIC DERIVATIVES: SYNTHESIS AND 13C NMR SPECTRA OF NEW SILYL AND STANNYL ISOXAZOLES
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Several new organometallic isoxazoles, silylated and stannylated in the heterocyclic ring or in a side chain have been made.Their 13C NMR spectra are consistent with the previous conclusions on the electronic effects of MR3 and CH2MR3 (M=Si, Sn) groups, and indicate the importance of the p?-d? and ?-? mechanisms in the various ring positions.
- Nesi, Rodolfo,Ricci, Alfredo,Taddei, Maurizio,Tedeschi, Piero,Seconi, Giancarlo
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p. 275 - 284
(2007/10/02)
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