- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
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We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
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- Ambulation of Incipient Proton during Gas-Phase Dissociation of Protonated Alkyl Dihydrocinnamates
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Upon activation in the gas phase, protonated alkyl dihydrocinnamates undergo an alcohol loss. However, the mechanism followed is not a simple removal of an alkanol molecule after a protonation on the alkoxy group. The mass spectrum of the m/z 166 ion for deuteron-charged methyl dihydrocinnamate showed two peaks of 1:5 intensity ratio at m/z 133 and 134 to confirm that the incipient proton is mobile. The proton initially attached to the carbonyl group migrates to the ring and randomizes before a subsequent transfer of one of the ring protons to the alkoxy group for the concomitant alcohol elimination. Moreover, protonated methyl dihydrocinnamate undergoes more than one H/D exchange. The spectra recorded from m/z 167 and 168 ions obtained for di- and tri-deuterio isotopologues showed peak pairs at m/z 134, 135 and 135, 136, at 1:2 and 1:1 intensity ratios, respectively, confirming the benzenium ion intermediate achieves complete randomization before the proton transfer. Additionally, protonated higher esters of alkyl dihydrocinnamates undergo a cleavage of the O-CH2 bond to form an ion/neutral complex, which, upon activation, dissociates generating a carbenium ion and dihydrocinnamic acid, or rearranges to generate protonated dihydrocinnamic acid and an alkene by a nonspecific proton transfer.
- Xu, Sihang,Zhang, Yong,Errabelli, Ramu,Attygalle, Athula B.
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p. 9468 - 9479
(2015/10/12)
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- A General and mild catalytic α-alkylation of unactivated esters using Alcohols
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Catalytic α-alkylation of esters with primary alcohols is a desirable process because it uses low-toxicity agents and generates water as the by-product. Reported herein is a NCP pincer/Ir catalyst which is highly efficient for α-alkylation of a broad scope of unactivated esters under mild reaction conditions. For the first time, alcohols alkylate unactivated α-substituted acyclic esters, lactones, and even methyl and ethyl acetates. This method can be applied to the synthesis of carboxylic acid derivatives with diverse structures and functional groups, some of which would be impossible to access by conventional enolate alkylations with alkyl halides. In a pinch: An NCP pincer/iridium catalyst is highly efficient for the α-alkylation of unactivated esters using alcohol under mild reaction conditions. The reaction is simple, clean, and scalable (1-10 mmol), and the scope with respect to the ester is wide.
- Guo, Le,Ma, Xiaochen,Fang, Huaquan,Jia, Xiangqing,Huang, Zheng
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supporting information
p. 4023 - 4027
(2015/03/30)
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- [IrCl(cod)]2-catalyzed direct oxidative esterification of aldehydes with alcohols
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[IrCl(cod)]2 catalyzed the oxidative esterification of a variety of aldehydes with methanol as a solvent in combination with K2CO3 under mild conditions (rt, 12 h). The oxidative esterification reaction of aliphatic aldehydes also took place with olefinic alcohols as reagents in toluene under similar conditions.
- Kiyooka, Syun-ichi,Wada, Yosuke,Ueno, Mahuyu,Yokoyama, Takeshi,Yokoyama, Reiko
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p. 12695 - 12701
(2008/03/14)
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- Iridium-catalyzed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols with precoordination of the double bond of alcohols to iridium
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A novel iridium-catalyzed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols in toluene was found under mild conditions of [IrCl(cod)]2 (5 mol %) in combination with K2CO 3 (10 mol %) at rt.
- Kiyooka, Syun-Ichi,Ueno, Mahuyu,Ishii, Eri
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p. 4639 - 4642
(2007/10/03)
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- THE INVENTION OF RADICAL REACTIONS PART XVIII. A CONVENIENT SOLUTION TO THE 1-CARBON PROBLEM (R-CO2H --> R-13CO2H)
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Radicals generated by photolysis (W light) of esters derived from N-hydroxy-2-thiopyridone react with electrophilic isocyanides 2a and (in the presence of trifluoroacetic acid) 2b to give adducts of type 3.Convenient reaction procedures have been worked out to hydrolyse the adducts to amides of type 5, from which the original acid can be regenerated under mild conditions.The three important acids oleic, linoleic and arachidonic have all given smooth reactions.In suitable examples, quantitative evolution of carbon dioxide and incorporation of 13C without dilution have been demonstrated.This reaction sequence will be useful for the labelling in the carboxyl group of prostaglandins, leukotrienes, and the side chain carboxyls of peptides.
- Barton, Derek H. R.,Ozbalik, Nubar,Vacher, Bernard
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p. 3501 - 3512
(2007/10/02)
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