- Effect of the Michael Acceptor in the Asymmetric Intramolecular Stetter Reaction
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The effect of different Michael acceptors was evaluated in the catalytic asymmetric intramolecular Stetter reaction. Utilizing a readily prepared chiral triazolium salt as a nucleophilic carbene precursor, the reactivity and selectivity of substrates containing different electron-deficient double bonds was shown to vary significantly under identical reaction conditions.
- Kerr, Mark S.,Rovis, Tomislav
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- Investigation of Straightforward, Photoinduced Alkylations of Electron-Rich Heterocompounds with Electron-Deficient Alkyl Bromides in the Sole Presence of 2,6-Lutidine
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Alkylations of simple electron-rich heterocompounds deliver valuable target structures in bioorganic and medicinal chemistry. Herein, we present a straightforward and photosensitizer free approach for the photoinduced C–C coupling of electron-rich unsaturated heterocompounds with alkyl bromides using 405 nm and 365 nm irradiation. Comprehensive mechanistic studies indicate the involvement of 2,6-lutidine in the formation of a non-covalently bound intermediate to which the function of a photosensitizer is attributed. UV/Vis spectra reveal the formation of a bathochromic shifted band when the electron-deficient alkyl bromide is mixed with the structural motif of 2,6-substituted pyridine. Upon photochemical excitation of this band, we find the initiation of the C–C bond-forming reaction. Using this approach highly versatile alkylation products, e.g. α-substituted ketones and 2-substituted furan, thiophene, and pyrrole derivatives, are obtained in high selectivity. Furthermore, this synthetic methodology can be applied to access substituted indoles, which cannot be obtained by other transformations.
- Fuks, Elina,Huber, Laura,Schinkel, Thea,Trapp, Oliver
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supporting information
p. 6192 - 6198
(2020/08/19)
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- Understanding the Scope of Feist–Bénary Furan Synthesis: Chemoselectivity and Diastereoselectivity of the Reaction Between α-Halo Ketones and β-Dicarbonyl Compounds
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Feist–Bénary furan synthesis, the reaction between α-halocarbonyl and β-dicarbonyl compounds, has been known as an efficient method for generating many different types of furans containing a carbonyl group at C-3. However, it has also been reported that, under similar reaction conditions, intermediate tricarbonyl species could be further converted to alternative furan isomers through the application of a Paal–Knorr synthesis. In this manuscript, we investigate the chemoselectivity and diastereoselectivity of furan synthesis from α-halo ketones and β-dicarbonyl compounds, by carrying out the separation and characterization of the intermediates involved in the reaction. Additionally, a one-pot Feist–Bénary furan synthesis from α-halo ketones and β-dicarbonyl compounds without any base or solvent has also been developed.
- Peng, Yi,Luo, Juan,Feng, Qiang,Tang, Qiang
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p. 5169 - 5179
(2016/10/26)
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- Air- and water-tolerant rare earth guanidinium BINOLate complexes as practical precatalysts in multifunctional asymmetric catalysis
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Shibasaki's REMB catalysts (REMB; RE = Sc, Y, La-Lu; M = Li, Na, K; B = 1,1′-bi-2-naphtholate; RE/M/B = 1/3/3) are among the most enantioselective asymmetric catalysts across a broad range of mechanistically diverse reactions. However, their widespread us
- Robinson, Jerome R.,Fan, Xinyuan,Yadav, Jagjit,Carroll, Patrick J.,Wooten, Alfred J.,Pericàs, Miquel A.,Schelter, Eric J.,Walsh, Patrick J.
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supporting information
p. 8034 - 8041
(2014/06/23)
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- Reactivity of 2-chloro- and 2-(tosyloxy)cyclohexanones towards anions electrogenerated at carbonium and nitrogen atoms. Electrochemically induced Favorskii rearrangement
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Carbonium and nitrogen anions were generated by cathodic reduction of 6, 7 and 8 or by deprotonation of 9 and 10 (by means of electrogenerated bases).Their reactivity towards α-substituted ketones 1 and 2 was studied.The reaction products 5b-d, 4b and 3 are formed according to the Favorskii rearrangement, substitution, and formal reduction mechanisms, respectively.In most cases, the reaction pathway appears to be driven by the applied electric potential.The Favorskii rearrangement undergone by 1 and 2 under electrochemical conditions can also be induced by nitrogen (Ph-NH--Ph) and carbonium (CH3COC-HCO2Et) anions, which have never been used before in this kind of reaction. - Keywords: probase / Favorskii rearrangement / electrogenerated anions / α-substituted cyclohexanones
- Angelis, F. De,Feroci M.,Inesi, A.
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p. 712 - 719
(2007/10/02)
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- CHEMISTRY OF α-NITROEPOXIDES: SYNTHESIS OF USEFUL INTERMEDIATES VIA NUCLEOPHILIC RING OPENING OF α-NITROEPOXIDES
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Various α-nitroepoxides are converted into corresponding 1,2-diketones via two different ways of ring opening viz. with Pd(O) and with DMSO/BF3*EtO2 (or ClSiMe3).In addition to this, a variety of nucleophiles are reacted with α-nitrocyclopentene oxide 6 and α-nitrocyclohexene oxide 7 to form the corresponding α-substituted ketones which are useful intermediates in organic synthesis.Two of the products so obtained viz. 32 and 33 are also transformed further into optically active thialactones 38 and 39 respectively via baker's yeast reduction followed by lactonisation.
- Vankar, Yashwant D.,Shah, Kavita,Bawa, Anita,Singh, Surendra P.
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p. 8883 - 8906
(2007/10/02)
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- Reaction with Umpolung of the Malonyl Radical
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The malonyl radical 3 can be generated from chloro- or bromomalonate in a radical chain reaction.This radical reacts with enol ethers 6 to addition products 7 or substitution products 10.During the formation of 7 the adduct radicals 12 are trapped by tin
- Giese, Bernd,Horler, Hans,Leising, Michael
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p. 444 - 452
(2007/10/02)
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- Malonate Anion Induced Favorskii-Type Rearrangement. Reaction of Cyclic α-Halo Ketones with Sodiomalonates
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The reaction of 2-chlorocyclohexanone (1b) with ethyl sodiomalonate in benzene at 0-25 deg C gave 6-bicyclohexan-6-ol (4c), the Favorskii-type intermediate, in 49percent yield, in place of the substitution product ethyl C-(2-oxocyclohexyl)malonate (3).Derivatives of bicycloheptan-7-ol (4a,b) and those of bicyclohexan-6-ol (4d,e) were also obtained in good yields by similar means.Compound 4c was transformed into 3 readily by heating with 0.05 equiv of NaH in benzene.The hydrolysis of 4a-d with 0.2 N NaOH followed by pyrolysis at 110-120 deg C gave the ring-contracted β-keto esters 9a-d.Pyrolysis after the hydrolysis with 2N NaOH gave the corresponding ketones 11a-d in good yields.Oxidation of 4c with CrO3 and HClO4 afforded ethyl C-(2-hydroxycyclopentanecarbonyl)malonate (14) in 45 percent yield.Treatment of 4c with Br2 gave ethyl C-(1-bromocyclopentanecarbonyl)malonate (18) in 64 percent yield.
- Sakai, Takashi,Amano, Eiichiro,Kawabata, Akifumi,Takeda, Akira
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