13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion
Abstract
1. Introduction
2. Electronic Effects of Heteroatoms on Aromatic Rings
2.1. Influence of Benzene Ring Substituents in the 13C NMR Chemical Shifts
2.2. Effect of Heteroatoms on 13C-NMR of Benzazoles
3. Estimation of the Anular Tautomerism on Benzimidazol
4. Tautomers and Mesomers in 1- and 2-Substituted Benzimidazoles
4.1. Effects of the Contribution of Mesomeric Structures in 1-Substituted Benzimidazoles
4.2. Effects of the Contribution of Tautomers in 2-Substituted Benzimidazoles
Compound | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solvent | Ref. |
---|---|---|---|---|---|---|---|---|---|
7 (R = Me) | 151.3 151.2 | 138.3 143.5 | 114.4 117.8 | 122.2 120.7 | 122.2 121.2 | 114.4 110.5 | 138.3 134.3 | CDCl3 DMSOd6 | [38] [33] |
7 (R = Et) | 157.4 | 139.4 | 114.7 | 122.7 | 122.7 | 114.7 | 139.4 | DMSOd6 | [33] |
7 (R = nPr) | 155.6 | 138.7 | 114.6 | 122.0 | 122.0 | 114.6 | 138.7 | CDCl3 | [33,39] |
7 (R = iPr) | 142.3 | 135.4 | 118.9 | 120.9 | 121.7 | 110.8 | 134.4 | DMSOd6 | [33] |
7 (R = Bn) | 151.8 | 133.2 | 114.0 | 125.8 | 125.8 | 114.0 | 133.2 | CDCl3 | [40] |
7 (R = Ph) | 151.8 | 144.4 | 119.4 | 123.0 | 122.2 | 111.8 | 135.5 | DMSOd6 | [31] |
8 (R = Me) | 147.7 | 143.5 | 122.1 | 123.8 | 122.1 | 112.1 | 126.6 | CDCl3 | [41] |
8 (R = Ph) | 147.7 | 143.9 | 122.3 | 126.5 | 123.8 | 112.0 | 133.9 | CDCl3 | [39] |
9 | 144.9 | 136.6 | 116.3 | 124.8 | 124.8 | 116.3 | 136.6 | DMSOd6 |
5. Iminothiol-Thioamide Tautomerism and Mesomers in 1,3-Benzoheterazolidine-2-thiones
5.1. Tautomers and Mesomers in Benzothiazolidine Tione
5.2. C4/C7 13C NMR Chemical Shifts of 1,3-Benzoheterazolidine-2-tiones in Iminothiol-Thioamide Tautomerism and Benzimidazolidine-2-selone Mesomerism
5.3. Mesomerism in N1-acyl-1,3-benzoheterazolidine-2-thiones
5.4. Tautomeric Equilibrium in Omeprazole
6. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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δ-13C | ||||||
---|---|---|---|---|---|---|
Comp. | C1a | C1 | C2 | C3 | C4 | C4a |
1 (X = O) | 124.2 | 120.6 | 122.6 | 127.0 | 111.6 | 156.2 |
2 (X = S) | 134.9 | 121.9 | 124.6 | 127.0 | 122.9 | 138.5 |
3 (X = NH) | 122.6 | 120.0 | 118.4 | 125.4 | 110.8 | 139.6 |
Comp. | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solv. | Ref. |
---|---|---|---|---|---|---|---|---|---|
1 (X = O) | 152.6 | 140.1 | 120.5 | 125.4 | 124.4 | 110.8 | 150.5 | CDCl3 | [25] |
2 (X = S) | 153.8 | 153.2 | 121.8 | 126.1 | 125.4 | 123.6 | 133.6 | CDCl3 | [25,26] |
140.5 | 137.1 | 115.3 | 121.3 | 121.3 | 115.3 | 137.1 | CDCl3 | [25,27] | |
141.1 | 137.4 | 114.8 | 122.7 | 122.1 | 114.8 | 137.4 | CD3OD | [28] | |
3 (X = NH) | 141.9 | 138.4 | 115.3 | 121.7 | 121.7 | 115.3 | 138.4 | DMSOd6 | [4] |
141.6 | 143.4 | 118.7 | 121.2 | 120.1 | 110.9 | 133.7 | HMPAd18 | [4] | |
142.6 | 143.0 | 119.9 | 122.1 | 123.0 | 112.2 | 136.1 | Solid | [4] | |
4 (X = NMe) | 143.9 | 143.7 | 120.4 | 123.1 | 122.2 | 109.5 | 134.7 | CDCl3 | [29] |
144.5 | 143.3 | 119.2 | 122.3 | 121.1 | 110.1 | 134.5 | DMSOd6 | [4] |
Comp. | C2 | C3a | C4 | C5 | C6 | C7 | C7a |
---|---|---|---|---|---|---|---|
3a/3b | 142.5 | 139.0 | 116.3 | 122.3 | 122.3 | 116.3 | 139.0 |
[3c/3d]+ | 143.6 | 133.8 | 118.3 | 130.0 | 130.0 | 118.3 | 133.8 |
[3d/3f]− Na+ | 153.1 | 146.9 | 116.4 | 116.7 | 116.7 | 116.4 | 146.9 |
[3d/3f]− Li+ | 153.5 | 147.0 | 116.8 | 117.0 | 117.0 | 116.8 | 147.0 |
Comp. | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solvent | Ref. |
---|---|---|---|---|---|---|---|---|---|
4 | 143.9 144.5 | 143.7 143.3 | 120.4 119.2 | 123.1 122.1 | 122.2 121.3 | 109.5 110.1 | 134.7 134.5 | CDCl3 DMSOd6 | [29] [4] |
5 | 144.0 151.6 | 142.2 143.8 | 120.6 119.0 | 123.6 122.1 | 122.7 121.2 | 110.4 116.5 | 133.7 134.8 | CDCl3 DMSOd6 | [32] [33] |
6 | 143.9 | 141.4 | 120.6 | 126.0 | 125.1 | 115.5 | 131.4 | CDCl3 | [34] |
Comp. | C2 | C4 | C5 | C6 | C7 | C7a | C3a | Solv. | Ref. | % Npr |
---|---|---|---|---|---|---|---|---|---|---|
10 | 180.8 181.8 | 110.2 113.2 | 124.5 119.2 | 125.4 121.6 | 110.5 106.7 | 148.8 151.0 | 130.3 145.4 | CDCl3 DMSOd6 | [51] | 93.7 68.0 |
11 | 189.7 | 112.3 | 124.0 | 127.0 | 121.6 | 141.2 | 129.3 | DMSOd6 | 77.0 | |
12 | 167.9 | 109.6 | 122.3 | 122.3 | 109.6 | 132.7 | 132.7 | DMSOd6 | 100 | |
13 | 168.3 | 118.3 | 123.4 | 123.4 | 110.1 | 132.6 | 130.8 | DMSOd6 | 8.4 | |
14 | 165.7 165.2 | 118.3 118.1 | 123.7 124.0 | 124.2 124.5 | 109.8 110.0 | 151.9 151.4 | 141.9 141.4 | CDCl3 DMSOd6 | [52] | 8.4 10.5 |
15 | 170.7 167.9 | 122.0 121.7 | 125.4 124.3 | 127.4 126.3 | 123.3 120.9 | 136.1 134.5 | 154.4 152.8 | CD3OD DMSOd6 | [52] | 0.0 2.4 |
16 | 151.9 151.2 152.3 | 113.7 113.6 117.8 | 121.7 121.2 121.9 | 121.7 121.2 121.9 | 113.7 113.6 110.9 | 139.5 139.7 136.4 | 139.5 139.7 144.5 | CDCl3 DMSOd6 (27 °C) DMF-d7 (−65 °C) | [53] | 56.8 57.9 13.7 |
17 | 153.2 152.6 | 118.0 117.4 | 121.8 121.2 | 121.8 121.2 | 108.3 109.2 | 136.8 136.9 | 143.3 142.9 | CDCl3 DMSOd6 | [54] | 11.6 17.9 |
Comp. | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solvent | Ref. | N4pr% |
---|---|---|---|---|---|---|---|---|---|---|
18 | 162.8 | 132.1 | 110.0 | 123.3 | 122.6 | 110.0 | 133.7 | DMSOd6 | [58] | 95.8 |
19 | 160.3 | 133.0 | 114.4 | 121.1 | 122.8 | 109.9 | 133.8 | DMSOd6 | [58] | 50.5 |
20 | 142.6 | 144.3 | 110.5 | 123.0 | 124.4 | 120.4 | 137.3 | CD2Cl2 | [58] | 90.5 |
21 | 145.6 | 145.3 | 114.1 | 121.8 | 121.9 | 118.8 | 136.8 | CD2Cl2 | [58] | 52.7 |
Comp. | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solvent | Npr% | Ref. |
---|---|---|---|---|---|---|---|---|---|---|
22 | 178.8 | 129.5 | 115.8 | 125.5 | 126.0 | 109.7 | 145.9 | DMSOd6 | 34.7 | [58] |
23 | 168.9 | 129.8 | 114.3 | 122.3 | 124.3 | 108.5 | 130.1 | DMSOd6 | 50.5 | [60] |
24 | 169.4 | 130.9 | 115.0 | 123.3 | 125.2 | 109.4 | 131.0 | DMSOd6 | 43.1 | [60] |
25 | 168.1 | 129.5 | 113.2 | 125.1 | 125.1 | 113.2 | 129.5 | CDCl3 | 62.1 | [61] |
Claramunt et al. | C2 | C3a | C4 | C5 | C6 | C7 | C7a | Solvent | Npr% |
---|---|---|---|---|---|---|---|---|---|
26a = 26b | 155.4 | 146.0 | 101.1 | 157.4 | 115.3 | 113.1 | 129.9 | THF-d8 | 63 |
26c = 26d | 153.5 | 140.2 | 121.6 | 114.2 | 158.2 | 94.0 | 136.5 | THF-d8 | 37 |
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García-Báez, E.V.; Padilla-Martínez, I.I.; Cruz, A.; Rosales-Hernández, M.C. 13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion. Molecules 2022, 27, 6268. https://doi.org/10.3390/molecules27196268
García-Báez EV, Padilla-Martínez II, Cruz A, Rosales-Hernández MC. 13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion. Molecules. 2022; 27(19):6268. https://doi.org/10.3390/molecules27196268
Chicago/Turabian StyleGarcía-Báez, Efrén V., Itzia I. Padilla-Martínez, Alejandro Cruz, and Martha C. Rosales-Hernández. 2022. "13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion" Molecules 27, no. 19: 6268. https://doi.org/10.3390/molecules27196268
APA StyleGarcía-Báez, E. V., Padilla-Martínez, I. I., Cruz, A., & Rosales-Hernández, M. C. (2022). 13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion. Molecules, 27(19), 6268. https://doi.org/10.3390/molecules27196268