- Vinyltriphenylphosphonium salt mediated synthesis of 1,4-benzoxazine and coumarin derivatives
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Protonation of the reactive 1:1 intermediate produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate by 2-aminophenol, 3-aminophenol, 4-aminophenol and 2-amino-3-hydroxypyridine leads to vinyltriphenylphosphonium salts, whi
- Yavari, Issa,Adib, Mehdi,Hojabri, Leila
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- Synthesis of extremely stable alkyl and hydride complexes of the type (R2NCS2)Pt(PEt3)R
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The reaction of (R2NCS2)Pt(PEt3)Cl (R = Me, Et), prepared from [Pt(PEt3)Cl2]2 and Na(R2NCS2), with alkyllithium or Grignard reagents yields (R2NCS2)Pt(PEt3)(alkyl) (alkyl = Me, n-Pr, i-Pr, n-Bu, sec-Bu, i-Bu, t-Bu) complexes. These new alkylplatinum complexes are very stable and can be heated in solution at 100°C for extended periods without decomposition. The reaction of (R2NCS2)Pt(PEt3)Cl with NaBH4 yields the stable complexes (R2NCS2)Pt(PEt3)H, which decompose only slowly at 110°C. This hydride (R = Me) does not react with ethylene or phenylacetylene but will react with MeO2CC≡CCO2Me to yield a mixture of the E and Z isomers of (Me2NCS2)Pt(PEt3)(η1-C(CO2Me)=C(H)CO2Me ). The reaction of (R2NCS2)Pt(PEt3)Cl with AgBF4 and ethylene yields [R2NCS2)Pt(PEt3)(C2H4)]BF4, but these complexes are very unstable, decomposing rapidly in the absence of ethylene.
- Reger,Baxter,Garza
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- Microwave-specific acceleration of a retro-Diels-Alder reaction
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A high-temperature retro-Diels-Alder reaction is accelerated by microwave (MW) heating to rates higher than expected based on Arrhenius kinetics and the measured temperature of the reaction mixture. Observations are consistent with selective MW heating of the polar reactant relative to other, less polar components of the reaction mixture.
- Dudley, Gregory B.,Frasso, Michael A.,Stiegman, Albert E.
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supporting information
p. 11247 - 11250
(2020/10/06)
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- Domino [4 + 1]-annulation of α,β-unsaturated δ-amino esters with Rh(ii)-carbenoids-a new approach towards multi-functionalized N-aryl pyrrolidines
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Catalytic decomposition of diazomalonates and other diazoesters using Rh(ii)- and Cu(ii)-complexes in the presence of α,β-unsaturated δ-(N-aryl)amino esters gives rise to the formation of multi-functionalized pyrrolidines with yields of up to 82%. The reaction apparently occurs as a domino process involving the initial N-ylide formation followed by intramolecular Michael addition to the conjugated system of amino esters to afford the pyrrolidine heterocycle. The whole process can also be classified as a [4 + 1]-annulation of the δ-amino α,β-unsaturated ester with the carbenoid intermediate. This journal is
- Medvedev,Galkina,Klinkova,Giera,Hennig,Schneider,Nikolaev
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supporting information
p. 2640 - 2651
(2015/06/08)
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- Three-component reaction of triphenylphosphine, dialkyl acetylenedicarboxylates, and heterocyclic rings and the related iminophosphoranes
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Crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reaction of triphenylphosphine, dialkyl acetylenedicarboxylate, and NH acids, such as 2-aminothiazole and 2-aminobenzothiazole. These stabilized phosphoranes undergo a
- Anary-Abbasinejad, Mohammad,Hassanabadi, Alireza,Khaksari, Zahra
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p. 204 - 212
(2011/10/31)
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- Ruthenium- and rhodium-catalyzed carbenoid reactions of diazoesters in hexaalkylguanidinium-based ionic liquids
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Hexaalkylguanidinium-based room-temperature ionic liquids were investigated as solvents for the cyclopropanation of styrene with diazoacetates catalyzed by Rh2(OAc)4 or [Ru2(μ-OAc) 2(CO)4]n. While the yields of the formed cyclopropanes are much lower compared to the reactions performed in dichloromethane, the diastereomeric ratio is not significantly affected by the change of the reaction medium. Immobilization of the catalysts is only partially successful. In contrast to this intermolecular reaction, the Ru-catalyzed formation of a β-lactam by an intramolecular carbenoid C-H insertion of an α-methoxycarbonyl-α-diazoacetamide occurs in high yield, similar to the Rh2(OAc)4-catalyzed reaction. The cis → trans isomerization of the resulting 1-tert-butyl-3-methoxycarbonyl-4-phenyl-azetidin- 2-one is accelerated in the ionic liquid N,N-dibutyl-N',N'-diethyl-N'',N''- dihexylguanidin-ium triflate.
- Large, Torsten,Mueller, Tobias,Kunkel, Helene,Buck, Stefan,Maas, Gerhard
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experimental part
p. 347 - 353
(2012/07/14)
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- Effect of imidazolium salts on the catalytic reaction of 1,3-dioxolanes with methyl diazoacetate
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Effect of imidazolium salts, [bmim]+Cl-, [bmim] +BF4 -, and [bmim]+PF6 -, on the reaction of 1,3-dioxolanes with methyl diazoacetate in the presence of copper-containing catalysts was studied. The product composition was found to depend on the reaction conditions and the nature and ratio of components of the catalytic system.
- Ivanova,Sultanova,Zlotskii
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experimental part
p. 106 - 108
(2011/06/18)
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- New catalytic system Cu(OAc)2-2,4-lutidine-ZnCl2 for olefin cyclopropanation with methyl diazoacetate
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A new efficient catalytic system consisting of Cu(OAc)2, 2,4-lutidine, and ZnCl2 was found for the cyclopropanation of unsaturated compounds with methyl diazoacetate. In the case of conjugated dienes, the process occurs regioselectively at the most alkylated C=C bond.
- Gareev,Sultanova,Biglova,Dokichev,Tomilov
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experimental part
p. 1784 - 1786
(2011/04/23)
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- Transfer semihydrogenation of alkynes catalyzed by a zero-valent palladium N-heterocyclic carbene complex
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(Chemical Equation Presented) Beyond Lindlar and without hydrogen: Transfer hydrogenation of internal alkynes catalyzed by a palladium(0) catalyst containing an N-heterocyclic carbene ligand gives Z alkenes without over-reduction to alkanes (see scheme). Contrary to most transfer hydrogenations, ketones are not reduced. As such, this is the first catalyst that shows excellent stereo- and chemo-selectivity for the semihydrogenation of alkynes without the need for hydrogen gas.
- Hauwert, Peter,Maestri, Giovanni,Sprengers, Jeroen W.,Catellani, Marta,Elsevier, Cornelis J.
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p. 3223 - 3226
(2008/12/23)
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- Synthesis of sulfur-containing aryliminophosphoranes
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Stabilized phosphoranes, obtained from the three-component reaction between dialkyl acetylenedicarboxylates and arylsulfonamides in the presence of triphenylphosphine, undergo a smooth intramolecular reaction, in boiling toluene to produce sulfur-containing iminophosphoranes in excellent yields.
- Yavari, Issa,Zabarjad-Shiraz, Nader,Bijanzadeh, Hamid R.
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p. 1381 - 1386
(2007/10/03)
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- Dirhodium(II) tetrakis(perfluoroalkylbenzoates) as partially recyclable catalysts for carbene transfer reactions with diazoacetates
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Three highly fluorinated dirhodium(II) tetrakis(benzoates), [Rh2(O2CRF)4, RF=C6H4-4-C6F13 (3) and C6H3-3,5-di(CnF2n+1) (n=6: 4; n=8: 5)], have been prepared and characterized. Only 4 and 5 are suited for applications in fluorous synthesis due to their excellent solubility in fluorous solvents. They were found to catalyze the following carbenoid reactions of diazo compounds in the fluorous solvents 1,1,2-trichloro-1,2,2-trifluoroethane and perfluoro(methylcyclohexane): cyclopropanation of styrenes using methyl diazoacetate, intermolecular carbene C-H insertion into hexane with methyl diazoacetate, and intramolecular aromatic C-H insertion of an α-diazo-β-ketoester. Except for the second reaction type, the catalyst could be recovered to a high extent by a liquid-liquid extraction (fluorous solvent - dichloromethane) due to its preference for the fluorous solvent. For the cyclopropanation reactions, the recovered catalyst was used in four subsequent reaction/workup cycles without significant loss of activity. In contrast, the catalyst could not be recovered from the carbenoid C-H insertion reaction with hexane; apparently, some by-products of this sluggish reaction, such as carbene dimers and oligomers, caused the deactivation or destruction of the catalyst.
- Endres, Andreas,Maas, Gerhard
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p. 3999 - 4005
(2007/10/03)
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- New highly fluorinated dirhodium(II) tetrakis(alkanecarboxylates) as catalysts for carbenoid C-H insertion reactions
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Six highly fluorinated dirhodium(II) tetrakis(alkanecarboxylates) [Rh2(OOCRF)4, RF = C7F15, CH2C6F13, CH2CH2C6F13, CH2CH2C8F17, CH2CH2C10F21, and CH2OCH2CH2C10F21] were prepared and characterized. Their suitability as catalysts for intermolecular carbenoid C-H insertion was investigated for the reaction of methyl diazoacetate with hexane. In the frame of fluorous synthesis, only Rh2(OOCC7F15)4 and Rh2(OOCCH2C6F13)4 are interesting, since they are soluble in perfluoro(methylcyclohexane) and catalyze the C-H insertion reaction more effectively than all other catalysts, including Rh2(OAc)4. The same two catalysts were also used to achieve 1,5-cyclization of an α-diazo-β-keto ester by intramolecular C-H insertion. Unfortunately, deterioration of the catalysts occurs to a significant extent during all reactions, and therefore, the possibilities to recover and reuse them are rather limited.
- Endres, Andreas,Maas, Gerhard
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p. 174 - 180
(2007/10/03)
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