- Atom-Economical and Tandem Conversion of Nitriles to N-Methylated Amides Using Methanol and Water
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A cobalt complex catalyzed tandem conversion of nitrile to N-methylated amide is described using a methanol and water mixture. Using this protocol, several nitriles were directly and efficiently converted to the desired N-methylated amides. Kinetic experiments using H2O18 and CD3OD suggested that water and methanol were the source of the oxygen atom and methyl group, respectively, in the final N-methylated amides. Importantly, the participation of active Co(I)-H species in this transformation was realized from the control experiment. The kinetic isotope effect (KIE) study suggested that the activation of the C-H bond of methanol was a kinetically important step. The Hammett plot confirmed that the reaction was faster with the electron deficient nitriles. In addition, the plausible pathway for the formation of N-methylated amides from the nitriles was supported by the computational study.
- Paul, Bhaskar,Maji, Milan,Kundu, Sabuj
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- Cobalt-Catalyzed 1,4-Aryl Migration/Desulfonylation Cascade: Synthesis of α-Aryl Amides
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A cobalt-catalyzed 1,4-aryl migration/disulfonylation cascade applied to α-bromo N-sulfonyl amides was developed. The reaction was highly chemoselective, allowing the preparation of α-aryl amides possessing a variety of functional groups. The method was used as the key step to synthesize an alkaloid, (±)-deoxyeseroline. Mechanistic investigations suggest a radical process.
- Gillaizeau-Simonian, Nicolas,Barde, Etienne,Guérinot, Amandine,Cossy, Janine
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p. 4004 - 4008
(2021/02/11)
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- Ruthenium-Catalyzed Synthesis of N-Methylated Amides using Methanol
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An efficient synthesis of N-methylated amides using methanol in the presence of a ruthenium(II) catalyst is realized. Notably, applying this process, tandem C-methylation and N-methylation were achieved to synthesize α-methyl N-methylated amides. In addition, several kinetic studies and control experiments with the plausible intermediates were performed to understand this novel protocol. Furthermore, detailed computational studies were carried out to understand the mechanism of this transformation.
- Paul, Bhaskar,Panja, Dibyajyoti,Kundu, Sabuj
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supporting information
p. 5843 - 5847
(2019/08/26)
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- Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: A kinetic study
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The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N 2 liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions.
- Akimoto, Ryo,Tokugawa, Takehiro,Yamamoto, Yutaro,Yamataka, Hiroshi
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experimental part
p. 4073 - 4078
(2012/06/29)
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