Esterification of Tertiary Amides: Remarkable Additive Effects of Potassium Alkoxides for Generating Hetero Manganese–Potassium Dinuclear Active Species

Abstract

A catalyst system of mononuclear manganese precursor 3 combined with potassium alkoxide served as a superior catalyst compared with our previously reported manganese homodinuclear catalyst 2 a for esterification of not only tertiary aryl amides, but also tertiary aliphatic amides. On the basis of stoichiometric reactions of 3 and potassium alkoxide salt, kinetic studies, and density functional theory (DFT) calculations, we clarified a plausible reaction mechanism in which in situ generated manganese–potassium heterodinuclear species cooperatively activates the carbonyl moiety of the amide and the OH moiety of the alcohols. We also revealed details of the reaction mechanism of our previous manganese homodinuclear system 2 a, and we found that the activation free energy (ΔG≠) for the manganese–potassium heterodinuclear complex catalyzed esterification of amides is lower than that for the manganese homodinuclear system, which was consistent with the experimental results. We further applied our catalyst system to deprotect the acetyl moiety of primary and secondary amines.

Fifty Shades of Phenanthroline: Synthesis Strategies to Functionalize 1,10-Phenanthroline in All Positions

“…The Mn complex of 830 has been used to perform the esterification of tertiary amides (Scheme 158, Hirai et al). 747 DMF is used as a pronucleophile, degrading into dimethylamine in the reaction conditions. This trick permits the use of very volatile dimethylamine (ebullition point at 7 °C) to be avoided.…”

“…When using 3-dimethylaminopropylamine and heating the reaction in an oil bath at 140–150 °C for 4 h, the product 830 (Scheme , Molock et al) is obtained with 89% yield (using microwave irradiation, the yield was 60%). The Mn complex of 830 has been used to perform the esterification of tertiary amides (Scheme , Hirai et al) . DMF is used as a pro-nucleophile, degrading into dimethylamine in the reaction conditions.…”

“…Various aliphatic amines (Scheme ) or N-containing heterocycles (Scheme ) have been used as nucleophiles. 2-Aminoethanol, methylamine, ammoniac, 1,2-dimethylalkanediamine, various diaminoalkanes, bis­(2-methoxyethyl)­amine, and even poorly nucleophilic DMF have been used to perform the nucleophilic substitution on 4,7-dihalogenated phen under either microwave irradiation or conventional heating (refs , , , , − , and − ). For example, the obtained ligands were used for the copper-catalyzed N -arylation of purines (Scheme , Larsen et al) or as G-quadruplex stabilizers (Scheme , Nielsen et al) .…”

Direct esterification of amides by the dimethylsulfate-mediated activation of amide C–N bonds

“…To address this limitation, various methods have been devised for the esterification of amides. Transition metal-catalyzed reactions can be considered as one of the most effective methods for achieving this goal 14 – 19 , as shown in Fig. 1a .…”

Hydrolysis of amide bonds in dipeptides and nylon 6 over a ZrO2 catalyst

“…24 Mn-containing complexes were also reported as effective catalysts for the esterification of tertiary amides. 25,26 For the hydrolysis of nylon 6 (also called polyamide-6) as an example of polyamides, high-temperature water typically at 573 K or above produced its monomer as a cyclic form (i.e., -caprolactam) and/or linear form (i.e., -aminocaproic acid) in up to 92% yield (Table S3). 4,[27][28][29][30][31][32][33][34] The use of acids enabled to decrease the reaction temperature to a certain or large extent; some of them including solid acids such as H-Beta zeolites and sulfated -Al 2 O 3 -ZrO 2 32,34 were reported to work as catalysts possibly owing to the production of -caprolactam, which possesses neither carboxy group nor amino group, instead of -aminocaproic acid.…”