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CC BY-NC-ND 4.0 · SynOpen 2021; 05(04): 294-300
DOI: 10.1055/a-1661-5655
DOI: 10.1055/a-1661-5655
letter
Ru-Catalyzed Selective C–H Functionalization of Pyridotriazoles with Acrylates
Abhisek Joshi
,
Rashmi Semwal
,
S. R. is grateful to the Department of Science and Technology, Ministry of Science and Technology, India (DST) for the award of an INSPIRE Fellowship. We also thank CSIR-CSMCRI (Grant Numbers MLP-0027 and MLP-320) for partial financial support.
Abstract
Ruthenium-catalyzed efficient and selective C–H alkenylation of pyridotriazoles with acrylates is described. The combination of metals (Ru and Fe) plays a crucial role in achieving quantitative yields of the desired products. The reaction is proposed to involve the formation of a ruthenium cyclometalated intermediate.
Supporting Information
- Supporting information for this article is available online at https://doi.org/10.1055/a-1661-5655.
- Supporting Information
Publication History
Received: 23 September 2021
Accepted after revision: 04 October 2021
Accepted Manuscript online:
05 October 2021
Article published online:
13 October 2021
© 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Georg Thieme Verlag KG
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-
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10
Experimental SectionAll commercially available chemicals and reagents were used without any further purification unless otherwise indicated. 1H and 13C NMR spectra were recorded at 600, 200, 150, and 125 MHz, respectively. Spectra were recorded in CDCl3 as solvent. Multiplicity is indicated as follows: s (singlet), d (doublet), t (triplet), m (multiplet), dd (doublet of doublets), and coupling constants (J) are given in Hz. Chemical shifts are reported in ppm relative to TMS as an internal standard. Mass spectra were obtained using electron impact (EI) ionization. Progress of the reactions was monitored by thin-layer chromatography (TLC). All products were purified through column chromatography using silica gel with 100–200 mesh size using ethyl acetate/hexane as eluent unless otherwise stated.General Procedures(A) Synthesis of Triazolopyridine Derivatives 1Hydrazine monohydrate (0.30 mmol) and acetic acid (0.02 mmol) were added to a solution of the requisite 2-acylpyridine (0.20 mmol) in ethanol (1.0 mL) at room temperature. The reaction mixture was heated at reflux for 6 h, and then EtOAc (5.0 mL) and Cu(OAc)2 (0.01 mmol) were added. After stirring at the indicated temperature for the indicated time, the resulting mixture was cooled to room temperature and then diluted with EtOAc (20 mL). The organic phase was washed with water (10 mL) and then dried over anhydrous Na2SO4. After filtration and concentration under reduced pressure, followed by purification by column chromatography, the desired triazolopyridine derivatives were isolated.(B) Synthesis of Methyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3a)To a reaction tube equipped with a magnetic stir bar, 3-phenyl[1,2,3]triazolo[1,5-a]pyridine (1a, 48.8 mg, 0.25 mmol), methyl acrylate (2a, 43.1 mg, 0.5 mmol), [RuCl2(p-cymene)]2 (6.75 mg, 5 mol%), FeCl3 (81.1 mg, 0.5 mmol), and base KOAc (24.5 mg, 0.25 mmol) were added, followed by dry 1,4-dioxane (1 mL). The mixture was heated in a carousel reaction station at 140 °C in a closed tube for 48 h, and progress was monitored by TLC. After completion of reaction, it was allowed to cool to room temperature. Then the mixture was poured into brine (30 mL). The product was extracted with EtOAc (3 × 15 mL) and dried with anhydrous Na2SO4. After filtration and removal of solvent under reduced pressure the residue was purified by column chromatography using silica gel (20% EtOAc/hexane) to afford 3a (62.8 mg, 90% yield).Characterization Data
Methyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3a)Yield (62.8 mg, 90% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.80 (d, J = 7.2 Hz, 1 H), 7.89 (d, J = 16.0 Hz, 1 H), 7.81 (d, J = 7.7 Hz, 1 H), 7.66–7.64 (m, 2 H), 7.53 (t, J = 7.4 Hz, 1 H), 7.49 (d, J = 7.2 Hz, 1 H), 7.31–7.27 (m, 1 H), 7.06 (t, J = 6.8 Hz, 1 H), 6.51 (d, J = 16.0 Hz, 1 H), 3.73 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 167.1, 143.2, 136.6, 133.4, 132.0, 131.2, 130.8, 130.1, 128.7, 127.1, 125.8, 125.5, 119.3, 118.1, 115.5, 51.6. ESI-HRMS: m/z [M + Na]+ calcd for C19H15NONa: 302.0900; found: 302.0898.Ethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3b)Yield (52.8 mg, 72% yield, semisolid), eluent 20% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.79 (dd, J = 6.9, 2.7 Hz, 1 H), 7.85 (d, J = 16.0 Hz, 1 H), 7.80 (d, J = 7.7 Hz, 1 H), 7.66 (dd, J = 15.4, 8.1 Hz, 2 H), 7.52–7.49 (m, 1 H), 7.47 (t, J = 7.4 Hz, 1 H), 7.28 (d, J = 6.9 Hz, 1 H), 7.03 (t, J = 6.9 Hz, 1 H), 6.49 (d, J = 15.4 Hz, 1 H), 4.19–4.15 (m, 2 H), 1.25 (td, J = 6.9, 1.9 Hz, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.6, 143.0, 136.6, 133.4, 132.0, 131.2, 130.8, 130.1, 128.7, 127.1, 125.8, 125.5, 119.8, 118.1, 115.4, 60.4, 14.2. ESI-HRMS: m/z [M + Na]+ calcd for C17H15N3O2Na: 316.1056; found: 316.1056.Butyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3c)Yield (69.1 mg, 86% yield, semisolid), eluent 20% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.79 (d, J = 7.1 Hz, 1 H), 7.83–7.79 (m, 2 H), 7.67 (d, J = 7.3 Hz, 1 H), 7.63 (d, J = 8.9 Hz, 1 H), 7.53–7.450 (m, 1 H), 7.48 (t, J = 7.5 Hz, 1 H), 7.29–7.26 (m, 1 H), 7.04 (q, J = 7.1 Hz, 1 H), 6.50 (d, J = 15.9 Hz, 1 H), 4.13 (t, J = 6.5 Hz, 2 H), 1.61–1.55 (m, 2 H), 1.34–1.24 (m, 2 H), 0.91–0.86 (m, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.7, 142.9, 142.2, 136.6, 133.4, 132.0, 131.2, 130.9, 130.1, 128.7, 128.1, 127.0, 125.8, 125.5, 120.7, 119.8, 118.1, 115.4, 64.3, 30.6, 19.1, 19.0, 13.7. GC–MS: m/z [M] calcd for C19H19N3O2: 321.1477; found: 321.00.Methyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)-2-methylacrylate (3d)Yield (63.8 mg, 87% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.76 (d, J = 7.1 Hz, 1 H), 7.71–7.70 (m, 1 H), 7.63 (s, 1 H), 7.55 (d, J = 8.7 Hz, 1 H), 7.50–7.46 (m, 3 H), 7.25–7.22 (m, 1 H), 7.01 (t, J = 6.7 Hz, 1 H), 3.68 (s, 3 H), 2.06 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 167.1, 166.7, 143.7, 143.6, 141.0, 134.8, 133.9, 130.8, 130.7, 130.5, 129.8, 129.2, 129.1, 128.4, 127.9, 124.0, 122.9, 120.4, 112.8, 52.5, 29.8. GC–MS: m/z [M] calcd for C17H15N3O2: 293.1164; found: 293.10.2-Methoxyethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3e)Yield (65.5 mg, 81% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.83 (d, J = 7.0 Hz, 1 H), 7.84 (s, 1 H), 7.82–7.80 (m, 2 H), 7.65 (d, J = 8.5 Hz, 2 H), 7.53 (dd, J = 8.2, 1.8 Hz, 1 H), 7.36–7.32 (m, 1 H), 7.10 (t, J = 6.7 Hz, 1 H), 6.60 (d, J = 15.9 Hz, 1 H), 4.34–4.32 (m, 2 H), 3.65–3.63 (m, 2 H), 3.41 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.4, 142.4, 135.7, 135.1, 135.0, 132.2, 130.3, 129.8, 127.2, 126.3, 125.7, 120.7, 118.0, 115.7, 70.5, 63.8, 59.1. GC–MS: m/z [M] calcd for C18H17N3O3: 323.1270; found: 323.00.2-Hydroxyethyl (E)-3-(2-{[1,2,3]triazolo[1,5-a]pyridin-3-yl}phenyl)but-2-enoate (3f)Yield (56.6 mg, 70% yield, semisolid), eluent 50% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.76 (s, 1 H), 7.76 (d, J = 41.3 Hz, 2 H), 7.60 (s, 1 H), 7.51–7.48 (m, 3 H), 7.26 (s, 2 H), 7.01 (s, 1 H), 4.24 (s, 2 H), 3.78 (s, 2 H), 2.07 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 168.7, 139.2, 137.2, 134.7, 131.8, 130.8, 130.2, 128.8, 128.5, 128.1, 125.6, 118.4, 115.5, 66.6, 61.4, 14.2. GC–MS: m/z [M] calcd for C18H17N3O3: 323.1270; found: 323.00.2,2,2-Trifluoroethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3g)Yield (78.0 mg, 90% yield, semisolid), eluent 10% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.80 (d, J = 7.1 Hz, 1 H), 8.02 (d, J = 15.9 Hz, 1 H), 7.83 (d, J = 7.9 Hz, 1 H), 7.69 (d, J = 7.8 Hz, 1 H), 7.65 (d, J = 8.9 Hz, 1 H), 7.55 (t, J = 7.7 Hz, 1 H), 7.49 (d, J = 7.6 Hz, 1 H), 7.31–7.28 (m, 1 H), 7.06 (t, J = 6.8 Hz, 1 H), 6.56 (d, J = 16.0 Hz, 1 H), 4.55 (q, J = 8.2 Hz, 2 H). 13C NMR (150 MHz, CDCl3): δ = 165.0, 164.2, 146.9, 145.8, 136.4, 132.9, 132.1, 131.7, 130.8, 130.3, 129.6, 129.4, 129.1, 128.9, 128.0, 127.4, 126.7, 126.2, 125.7, 125.7, 125.6, 125.5, 124.0, 122.2, 118.5, 118.2, 118.0, 117.4, 115.6, 115.6, 60.7, 60.4, 60.2, 60.0. GC–MS: m/z [M] calcd for C17H12F3N3O2: 347.0882; found: 347.00.(E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylonitrile (3h)Yield (56.0 mg, 91% yield, semisolid), eluent 30% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.82 (d, J = 7.0 Hz, 1 H), 7.77 (d, J = 16.8 Hz, 1 H), 7.72 (d, J = 7.8 Hz, 1 H), 7.69 (d, J = 8.7 Hz, 1 H), 7.64 (d, J = 7.6 Hz, 1 H), 7.57 (t, J = 7.5 Hz, 1 H), 7.50 (t, J = 7.5 Hz, 1 H), 7.36–7.33 (m, 1 H), 7.09 (t, J = 6.9 Hz, 1 H), 5.94 (d, J = 17.0 Hz, 1 H). 13C NMR (150 MHz, CDCl3): δ = 149.3, 136.1, 132.7, 132.0, 131.0, 130.8, 130.6, 130.6, 128.8, 126.5, 126.3, 125.6, 118.1, 117.7, 115.7, 97.5. GC–MS: m/z [M] calcd for C15H10N4: 246.0905; found: 246.20.2-Ethylhexyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}phenyl)acrylate (3i)Yield (60.6 mg, 67% yield, yellow liquid), eluent 15% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.80–8.79 (m, 1 H), 7.78–7.72 (m, 2 H), 7.62 (t, J = 8.7 Hz, 2 H), 7.49 (dd, J = 8.1, 2.3 Hz, 1 H), 7.31–7.29 (m, 1 H), 7.06 (t, J = 6.5 Hz, 1 H), 6.51 (d, J = 16.1 Hz, 1 H), 4.07 (qd, J = 10.9, 5.7 Hz, 2 H), 1.56 (t, J = 6.0 Hz, 1 H), 1.31–1.24 (m, 11 H), 0.88–0.83 (m, 8 H). 13C NMR (150 MHz, CDCl3): δ = 166.6, 141.6, 135.7, 135.1, 134.9, 132.2, 132.1, 130.2, 129.8, 127.1, 126.2, 125.7,
121.1, 118.0, 115.6, 67.1, 38.8, 30.4, 29.0, 23.8, 23.0, 14.1, 11.1. GC–MS: m/z [M] calcd for C23H27N3O2: 377.2103; found: 377.30.Methyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylate (4a)Yield (65.1 mg, 83% yield, semisolid), eluent 25% ethyl acetate/hexane). 1H NMR (600 MHz, CDCl3): δ = 8.80 (d, J = 7.0 Hz, 1 H), 7.81–7.76 (m, 2 H), 7.61–7.58 (m, 2 H), 7.49 (d, J = 8.1 Hz, 1 H), 7.32–7.30 (t, J = 6.0 Hz, 1 H), 7.06 (d, J = 6.8 Hz, 1 H), 6.50 (d, J = 16.1 Hz, 1 H), 3.73 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.7, 141.9, 135.5, 135.0, 134.8, 132.0, 130.1, 129.6, 127.1, 126.2, 125.6, 120.5, 117.8, 115.6, 51.8. GC–MS: m/z [M] calcd for C16H12ClN3O2: 313.0618; found: 313.00.Ethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylate (4b)Yield (61.3 mg, 75% yield, semisolid), eluent 20% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.77 (s, 1 H), 7.84–7.79 (m, 2 H), 7.65 (s, 2 H), 7.50–7.46 (m, 2 H), 7.27 (s, 1 H), 7.02 (s, 1 H), 6.49 (d, J = 15.7 Hz, 1 H), 4.17 (s, 2 H), 1.24 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.8, 143.1, 136.7, 133.6, 132.2, 131.4, 131.0, 130.2, 128.9, 127.2, 125.9, 125.6, 120.0, 118.3, 115.6, 60.5, 14.4. ESI-HRMS: m/z [M + Na]+ calcd for C17H14ClN3O2Na: 350.0667; found: 350.0632.Butyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylate (4c)Yield (76.5 mg, 86% yield, semisolid), eluent 20% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.80 (d, J = 7.1 Hz, 1 H), 7.82 (d, J = 7.8 Hz, 1 H), 7.68 (d, J = 7.3 Hz, 1 H), 7.64 (d, J = 8.9 Hz, 1 H), 7.54 (t, J = 7.4 Hz, 1 H), 7.49 (t, J = 7.5 Hz, 1 H), 7.30–7.27 (m, 1 H), 7.05 (t, J = 6.8 Hz, 1 H), 6.51 (d, J = 15.9 Hz, 1 H), 4.14 (t, J = 6.5 Hz, 2 H), 1.62–1.58 (m, 2 H), 1.36–1.33 (m, 2 H), 0.92–0.88 (m, 3 H). 13C NMR (150 MHz, CDCl3): δ = 160.0, 159.3, 156.9, 143.9, 138.1, 136.8, 136.2, 130.2, 129.1, 127.6, 122.3, 120.9, 120.5, 114.9, 114.4, 114.3, 113.9, 112.1, 105.4, 55.3, 32.4, 31.2, 30.3. GC–MS: m/z [M] calcd for C19H18ClN3O2: 355.1058; found: 355.10.Methyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)-2-methylacrylate (4d)Yield (67.2 mg, 82% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.77 (d, J = 7.1 Hz, 1 H), 7.72–7.70 (m, 1 H), 7.64 (s, 1 H), 7.56 (d, J = 8.7 Hz, 1 H), 7.51–7.49 (m, 1 H), 7.48 (d, J = 3.3 Hz, 1 H), 7.25 (t, J = 7.32 Hz, 1 H), 7.02 (t, J = 6.7 Hz, 1 H), 3.69 (s, 3 H), 2.07 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 160.0, 134.8, 131.2, 129.9, 129.0, 128.5, 126.5, 124.8, 124.2, 123.0, 121.7, 121.0, 115.0, 114.3, 109.2, 55.5, 29.7. GCMS: m/z [M] calcd for C17H14ClN3O2: 327.0775; found: 327.05.2-Methoxyethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylate (4e)Yield (69.8 mg, 78% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.79 (d, J = 7.0 Hz, 1 H), 7.80–7.76 (m, 2 H), 7.60 (d, J = 8.5 Hz, 2 H), 7.49 (dd, J = 8.2, 1.8 Hz, 1 H), 7.32–7.28 (m, 1 H), 7.06 (t, J = 6.7 Hz, 1 H), 6.56 (d, J = 15.9 Hz, 1 H), 4.30–4.28 (m, 2 H), 3.61–3.59 (m, 2 H), 3.37 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 166.2, 142.2, 135.5, 134.9, 134.8, 132.0, 130.2, 129.7, 127.1, 126.2, 125.6, 120.5, 117.8, 115.6, 70.4, 63.7, 59.0. GC–MS: m/z [M] calcd for C18H16ClN3O3: 357.0880; found: 357.10.2-Hydroxyethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)but-2-enoate (4f)Yield (58.1 mg, 65% yield, semisolid), eluent 45% ethyl acetate/hexane). 1H NMR (600 MHz, CDCl3): δ = 8.83 (d, J = 7.1 Hz, 1 H), 7.84–7.80 (m, 2 H), 7.65 (d, J = 8.6 Hz, 2 H), 7.53 (d, J = 8.3 Hz, 1 H), 7.36–7.32 (m, 1 H), 7.10 (t, J = 6.8 Hz, 1 H), 6.60 (d, J = 15.8 Hz, 1 H), 4.33 (t, J = 4.7 Hz, 2 H), 3.65 (t, J = 4.7 Hz, 2 H), 3.41 (s, 3 H). 13C NMR (150 MHz, CDCl3): δ = 168.7, 139.2, 137.2, 134.6, 131.8, 130.8, 130.2, 128.7, 128.5, 128.1, 125.6, 118.4, 115.5, 66.6, 61.4, 14.2. GC–MS: m/z [M] calcd for C18H16ClN3O3: 357.0880; found: 357.10.2,2,2-Trifluoroethyl (E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylate (4g)Yield (84 mg, 88% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.71 (d, J = 7.2 Hz, 1 H), 7.93 (d, J = 16.0 Hz, 1 H), 7.75 (d, J = 8.0 Hz, 1 H), 7.60 (d, J = 8.0 Hz, 1 H), 7.57 (d, J = 9.0 Hz, 1 H), 7.48 (t, J = 7.6 Hz, 1 H), 7.42 (q, J = 7.8, 7.3 Hz, 1 H), 6.97 (t, J = 6.9 Hz, 1 H), 6.47 (d, J = 16.0 Hz, 1 H), 4.46 (q, J = 8.1 Hz, 2 H). 13C NMR (150 MHz, CDCl3): δ = 167.0, 166.6, 143.6, 143.5, 140.9, 134.7, 133.8, 130.7, 130.6, 130.4, 129.7, 129.1, 129.0, 128.3, 127.8, 123.9, 122.8, 120.3, 112.7, 52.4, 29.7. GC–MS: m/z [M] calcd for C17H11ClF3N3O2: 381.0492; found: 381.30.(E)-3-(2-{[1,2,3]Triazolo[1,5-a]pyridin-3-yl}-5-chlorophenyl)acrylonitrile (4h).Yield (60.4 mg, 86% yield, semisolid), eluent 25% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.24 (d, J = 7.8 Hz, 1 H), 8.02 (d, J = 6.7 Hz, 1 H), 7.80 (d, J = 8.0 Hz, 1H ), 7.72 (d, J = 9.2 Hz, 1 H), 7.48 (t, J = 7.5 Hz, 2 H), 7.39 (t, J = 7.5 Hz, 1 H), 7.20 (t, J = 7.9 Hz, 1 H), 6.81 (t, J = 6.7 Hz, 1 H). 13C NMR (150 MHz, CDCl3): δ = 149.3, 145.7, 140.1, 128.9, 125.3, 125.2, 124.3, 124.1, 124.0, 122.4, 121.5, 118.2, 111.9. GC–MS: m/z [M] calcd for C15H9ClN4: 280.0516; found: 280.0.Phenyl(pyridin-2-yl)methanone (5)11
Yield (14.0 mg, 31% yield, white solid), mp 42–44 ℃), 5% ethyl acetate/hexane. 1H NMR (600 MHz, CDCl3): δ = 8.71 (d, J = 4.3 Hz, 1 H), 8.07 (d, J = 7.7 Hz, 2 H), 8.03 (d, J = 7.8 Hz, 1 H), 7.88 (t, J = 7.7 Hz, 1 H), 7.58 (t, J = 7.3 Hz, 1 H), 7.47 (dd, J = 14.2, 6.9 Hz, 3 H). 13C NMR (150 MHz, CDCl3): δ = 193.7, 154.9, 148.4, 136.9, 136.1, 132.7, 130.8, 128.0, 126.0, 124.4.
- 11 Joshi A, Kumar R, Semwal R, Rawat D, Adimurthy S. Green Chem. 2019; 21: 962
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