- Selective electrochemical C[sbnd]O bond cleavage of β-O-4 lignin model compounds mediated by iodide ion
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The electrochemically oxidative cleavage of lignin β-O-4 model compounds mediated by iodide ion has been studied. The results indicate that electrolytic conditions play a predominant role in determining the distribution of cleavage products. The preparative-scale electrolysis proceeds in a simple undivided cell, employing a catalytic amount of NaI as the redox mediator and supporting electrolyte in methanol. Under these conditions, the Cβ[sbnd]O bond is selectively cleaved with 2,2-dimethoxy-2-arylacetaldehyde being the main product. In some cases, the reaction gives a good yield of cleavaged products. The results further demonstrate that the indirect electrolysis mediated by halide is a versatile approach for chemical transformation.
- Gao, Wei-Jing,Lam, Chiu Marco,Sun, Bao-Guo,Little, R. Daniel,Zeng, Cheng-Chu
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p. 2447 - 2454
(2017/04/03)
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- Reactions of α-Chloro- and α,α-dichloro-β-oxoaldehydes with Anionic Nucleophiles
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The reaction of α-chloro and α,α-dichloro-β-oxoaldehydes with anionic nucleophiles (NaOH, MeONa, PhONa, MeCOOK) proceeds mainly via haloform splitting with elimination of the formyl group; only with the most nucleophilic sodium methoxide, the reaction at the β-carbon atom partially occurs.The intermediate anions react with benzaldehyde to give difficulty accessible polyfunctional compounds.
- Guseinov, F. I.,Tagiev, S. Sh.,Moskva, V. V.
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- Thermolysis of 5-acyltriazolines. Formation of enamides. Reaction mechanism
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The thermolysis of 5-acyltriazolines 1, 2, 3 (X=COR', Y=CO2Me) was studied.Instead of the expected aziridines, enamides 5 to 8 were obtained by an unusual acyl migration.It has been shown that the reaction is intramolecular and proceeds via a 1,2 followed
- Said Ouali, Mohand,Vaultier, Michel,Carrie, Robert
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p. 809 - 814
(2007/10/02)
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- NOVEL SELECTIVE SYNTHESIS OF α-CHLOROMETHYL, α,α-DICHLOROMETHYL, AND α,α,α-TRICHLOROMETHYL KETONES FROM ALDEHYDE UTILIZING ELECTROREDUCTION AS KEY REACTIONS
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A variety of α-chloromethyl, α,α-dichloromethyl, and α,α,α-trichloromethyl ketones were synthesized from aldehyde utilizing cathodic reduction as key reactions.
- Shono, Tatsuya,Kise, Naoki,Yamazaki, Akira,Ohmizu, Hiroshi
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p. 1609 - 1612
(2007/10/02)
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- Pyrrole Annulation onto Aldehydes and Ketones via Palladium-Catalyzed Reactions
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α-Dicarbonyl systems reacted with vinylmagnesium bromide and acetic anhydride to give α-acetoxy-α-vinylalkanones.These substrates react with benzylamine in the presence of tetrakis(triphenylphosphine)palladium to give N-benzylpyrroles with substituents in the two and/or three position.The functiodifferentiated synthesis of α-dicarbonyl compounds from ketones makes this a pyrrole annulation onto any α-methylene carbonyl system.
- Trost, Barry M.,Keinan, Ehud
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p. 2741 - 2746
(2007/10/02)
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- Rearrangement of 1-Aryl-2,2-dihalo-1-alkanones
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Reaction of 1-aryl-2,2-dichloro-1-alkanones with alkoxides in the corresponding alcohol afforded a mixture of 1-aryl-2,2-dialkoxy-1-alkanones and 1-aryl-1,1-dialkoxy-2-alkanones.The mechanism was shown to proceed via α-chloro-α'-alkoxy epoxides, which rearranged into 1-alkoxy-1-aryl-1-chloro-2-alkanones, the latter giving the final compounds via either another epoxide intermediate or a solvolysis mechanism. α,α-Dibromo- and α-bromo-α-chloroalkyl aryl ketones behaved analogously, but α-bromo-α-fluoro- and α-chloro-α-fluoroalkyl aryl ketones gave exclusively solvolysis of initially formed 1-alkoxy-1-aryl-1-fluoro-2-alkanones, resulting in rearranged 1-aryl-1,1-dialkoxy-2-alkanones. α,α-Difluoroalkyl aryl ketones did not rearrange but underwent reduction of the carbonyl function on treatment with sodium methoxide in methanol.The influence of varying factors, such as the steric requirements of the alkoxide and the substrate, the concentration of the alkoxide, the aromatic substituent, the temperature, and the halogens, was investigated and correlated to the mechanism involved.
- Kimpe, Norbert De,Verhe, Roland,Buyck, Laurent De,Schamp, Niceas
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p. 2803 - 2813
(2007/10/02)
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