Acidity functions and the protonation of weak bases. Part VII. The protonation behaviour of dimethylaminopyridines and their N-oxides

Forsythe, P. P.; Frampton, Roger; Johnson, C. D.; Katritzky, Alan R.

doi:10.1039/p29720000671

Cited by 29 publications

(14 citation statements)

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“…The pathway for the catalytic reaction of A with B, summarized in Scheme 1, i±v, is analogous to the scheme proposed by Bruice for the chemical oxidation of amines by phenanthroquinones [2]. The pathway proposed by Bruice is consistent with the CV results described above, the known chemistry of DA [23], DA o-quinone [24,25] and DMAP [27,28], and the EC/PB/MS results described below. Other possible mechanisms [31] do not apply here.…”

Section: Catalytic Pathwaysupporting

confidence: 77%

“…DA orthoquinone was used here as the oxidant because of the importance of the redox reactions of DA/DA o-quinone redox couple with biological nucleophiles, and its neurochemical signi®cance. DMAP, a nonbiological amine, was chosen because of its strong nucleophilic character (pKa 1 9.70) [27], facilitating veri®cation of the catalytic pathway. In addition, DMAP has an oxidation potential higher than DA [28] aiding in the investigation of the catalytic oxidation.…”

Section: Introductionmentioning

confidence: 99%

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Real Time Characterization of Catalysis by On-Line Electrochemistry/Mass Spectrometry. Investigation of Quinone Electrocatalysis of Amine Oxidation

Regino

Brajter-Toth

1999

Electroanalysis

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Electrochemistry (EC) on-line with mass spectrometry (MS), with a particle beam (PB) liquid interface (EC/PB/MS), has been successfully applied to the investigation of the electrocatalytic type reaction, the oxidation of an amine, dimethylaminopyridine, by a quinone, dopamine. The investigation, of the reaction pathway, by EC/PB/MS supports catalytic type oxidation of the amine via formation of an intermediate quinone-amine adduct. EC/PB/MS allowed veri®cation of the reaction pathway, through the identi®cation of the intermediate, and the products of the oxidation, in close to real time, by EC/MS on-line. Oxidation of the adduct has been estimated as the limiting kinetic step in the reaction.

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Section: Catalytic Pathwaysupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Real Time Characterization of Catalysis by On-Line Electrochemistry/Mass Spectrometry. Investigation of Quinone Electrocatalysis of Amine Oxidation

Regino

Brajter-Toth

1999

Electroanalysis

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“…5 Since its discovery in the late 1960's, 6 DMAP and related compounds have been used in several areas of organic synthesis, including carbon-carbon bond-forming reactions. 7 As a consequence, recent works by Barbas, 8 Benaglia, 9 Palomo, 10 Luo,11 Carter, 12 and Nájera 13 prompted us to develop new types of DMAP-related organocatalysts.…”

mentioning

confidence: 99%

“…Michael donors such as ethyl 2-benzylacetoacetate (1d), ethyl 3-oxopentanoate (1e), and ethyl benzoylacetate (1f) and acceptors such as acrylonitrile (2b) ( Table 3, entries [3][4][5][6][7][8][9][10][11][12]. The decreased reactivity of the reactants 1d-1f with their increase in hydrophobicity might be accounted for by the difficulty to cause effective substrate interactions in water.…”

mentioning

confidence: 99%

Development of new DMAP-related organocatalysts for use in the Michael addition reaction of β-ketoesters in water

Nakano

Watanabe

et al. 2009

Tetrahedron Letters

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Abstract:A general and efficient protocol for the Michael addition reactions of β-ketoesters in pure water has been developed. The reactions are successfully catalyzed by newly designed DMAP-related organocatalysts such as 4-(didecylamino)pyridine, and the desired Michael adducts are obtained in good to high yields Keywords:Michael addition reaction; β-Ketoesters; DMAP-related organocatalyst, Aqueous media Organic reactions in water have received considerable attention from synthetic chemists, since they are environmentally clean, non-toxic and inexpensive. 1 In particular, over the past decade remarkable progress has been achieved in the field of organocatalytic transformations 2 in aqueous media as a primary contribution to "green chemistry". 3,4 However, there are still some limitations on the availability of organocatalysts and the versatility of reactions that might be effective "in pure water".In designing new water-tolerant organocatalysts, we were interested in the unique base character of 4-(dimethylamino)pyridine (DMAP, pK a 9.70 in H 2 O). There was a sharp contrast in the appearance of the reaction mixture in the respective experiments ( Figure 1). Thus, while the mixture containing 3d became an emulsion after the first 20-30 min of stirring, other compounds led to a substantially clear heterogeneous phase separation. We supposed that the attachment of two tails of an n-decyl chain to a 4-aminopyridine head should be "matched" to form a sort of hydrophobic media in water under such conditions, which allowed efficient catalysis to take place. To obtain further insight into the solvent effect of 3d-catalysis, we performed experiments using methyl cyclopentan-1-one-2-carboxylate (1b) as a Michael donor in various organic and water solvents (Table 2). In THF, CH 2 Cl 2 , and acetonitrile, the reaction proceeded very slowly and gave the adduct 4b in yields of 59-90% (Table 2, entries 1-3). The reaction in MeOH gave results that were almost comparable to those in water, 20 but the latter solvent was still advantageous with respect to its environmental friendliness and the reaction rate (Table 2, entries 4 and 5). 21< Table 2 > With these results in hand, we then investigated the general scope of this method. Thus, various β-ketoesters 1 were treated with Michael acceptors 2 in the presence of a catalytic amount of 3d under the standardized conditions. In all of the cases examined, the 3a-catalyzed reactions are also shown for comparison (Table 3).< Table 3 > When the reaction of ethyl 2-methylacetoacetate (1c) with 2a was performed in the presence of 10 mol% of 3d, the desired adduct 4c was obtained in 88% yield after stirring for 7.5 h, while the use of 3a resulted in an incomplete reaction even after 23 h, and gave 4c in only 15% yield (Table 3, entries 1 and 2). Very similar behavior was observed for otherMichael donors such as ethyl 2-benzylacetoacetate (1d), ethyl 3-oxopentanoate (1e), and ethyl benzoylacetate (1f) and acceptors such as acrylonitrile (2b) ( Table 3, entries 3-12). The decreased react...

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“…In the case of the N-oxides of 2-and 4-aminopyridines, also containing two potential electron-donating centers but found in conjugation, the oxygen atom of the N O group is protonated first [20,[31][32][33] (in the unoxidized analogs, the nitrogen atom of the heterocycle is first). In the absence of conjugation between the N O and amino groups in the N-oxide of 3-aminopyridine [20] protonation is effected at the oxygen atom, and in the N-oxide of 3-dimethylaminopyridine [34] at the nitrogen atom of the NMe 2 group, i.e.…”

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confidence: 99%

The effect of electronic factors on the reactivity of heteroaromatic N-oxides

Andreev

2010

Chem Heterocycl Comp

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On the basis of an analysis of the reasons for the multiplicity of constants for substituents it has been concluded that they are variables, the absolute value and sign of which depend on the nature of the compounds being considered (in particular other substituents), the partner with which reaction occurs, and the medium (the aggregate state of participants of the interaction). The use of modifications of the Hammett equation is caused by the impossibility in principle of only varying the values and sign of to describe universally linear functions of the dependence of rate (or equilibrium) constants of chemical processes from the algebraic sum of the electronic, steric, and other factors, which differ in their nature.At the present time empirical equations of the Hammett and Taft type (log(k/k 0 ) = ) are widely used in organic chemistry in spite of the fact that the multiplicity of constants requires greater care in choosing them for making correlations, and the use for interpreting the structure of a transition state interferes with certain other resistant concepts [1-6]. Thus the Hammett equation is used for assessing the structure of a transition state (according to the size of ) among similar compounds by the variation of substituents and consequently by the change in reactivity. It is therefore assumed that is a constant (but is dependent on the nature of the second reactant and the reaction conditions), i.e. the nature ( ) of a substituent does not affect the structure of the transition state. However according to the Hammond postulate [5] in rapid reactions the transition state is more like the reactants, but in slow reactions it is more like the reaction products, i.e. on changing the reaction rate the structure of the transition state must also be changed.In the monograph [4] V. A. Palm notes that the problem of constructing a precise scale even for induction constants of substituents of the type of functional groups or containing functional groups has no solution. The assumption of even O. A. Reutov, A. L. Kurts, and K. P. Butin [5, Vol. 1, p. 288], that " and are not independent parameters, as suggested, but are linked to one another, while a parameter linking and is reduced in their product", does not only not clarify the situation, but also remains as an additional problem as to the nature of this parameter.

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Acidity functions and the protonation of weak bases. Part VII. The protonation behaviour of dimethylaminopyridines and their N-oxides

Cited by 29 publications

References 0 publications

Real Time Characterization of Catalysis by On-Line Electrochemistry/Mass Spectrometry. Investigation of Quinone Electrocatalysis of Amine Oxidation

Real Time Characterization of Catalysis by On-Line Electrochemistry/Mass Spectrometry. Investigation of Quinone Electrocatalysis of Amine Oxidation

Development of new DMAP-related organocatalysts for use in the Michael addition reaction of β-ketoesters in water

The effect of electronic factors on the reactivity of heteroaromatic N-oxides

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