DRUG APPROVALS BY DR ANTHONY MELVIN CRASTO
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DOI: 10.1039/C7QO00945C, Research Article
Palladium-catalyzed direct ethoxycarbonylation with diethyl azodicarboxylate was developed and its reaction mechanism was explored by using DFT calculations.
Palladium-catalyzed direct C–H ethoxycarbonylation of 2-aryl-1,2,3-triazoles and efficient synthesis of suvorexant
Abstract
Efficient palladium-catalyzed C–H ethoxycarbonylation of 2-aryl-1,2,3-triazoles was developed by using diethyl azodicarboxylate as the esterification reagent. A wide variety of aryl esters containing 1,2,3-triazoles were obtained in moderate to good yields. In addition, density functional theory calculations were used to enhance the mechanistic studies.
3ea
5-methyl-2-(2H-1,2,3-triazol-2-yl)benzoate
Yellow oil, 1H NMR (600 MHz, Chloroform-d) δ 7.81 (s, 2H), 7.69 – 7.57 (m, 2H), 7.41 (d, J = 8.1 Hz, 8 1H), 4.20 (q, J = 7.1 Hz, 2H), 2.45 (s, 3H), 1.15 (t, J = 7.1 Hz, 3H); 13C NMR (100 MHz, Chloroformd) δ 166.8, 138.8, 136.1, 135.3, 132.2, 130.4, 127.2, 124.4, 61.4, 13.9; IR (cm-1): 2923, 2861, 1723, 1509, 1463, 1410, 1366, 1303, 1285, 1269, 1234, 1201, 1108, 1072, 1044, 1021, 962, 952, 158, 824, 778, 734, 630; HRMS (ESI) Calcd. for C12H13N3O2 [M+Na]+ 254.0905, found 254.0904.
To a round bottom flask charged 4-methyl-2-(2H-1,2,3-triazol-2-yl)benzoate (50 mg, 0.22 mmol), KOH (67.2 mg, 1.2 mmol), EtOH (3 ml) and H2O (0.5 ml), and the system was react at 40 oC for 5 h, and then cooled down to ambient temperature. The pH was adjusted to 1 with 5% HCl, and EtOH was removed under reduced pressure. The residual solvent was extracted with EtOAc (3 x 10 ml), and the solvent was evaporated under reduced pressure. The oily residue was purified by chromatography on a silica gelcolumn (DCM/MeOH) and product 4 was obtained with 90% yield. Suvorexant was synthesised from 4 and 5 according to the literature as previous report. [4, 5] Product 4: 5-methyl-2-(2H-1,2,3-triazol-2-yl)benzoic acid: 1H NMR (400 MHz, Chloroform-d) δ 7.83 (s, 2H), 7.76 (d, J = 2.0 Hz, 1H), 7.64 (d, J = 8.2 Hz, 1H), 7.50 – 7.42 (m, 1H), 2.47 (s, 3H). [4, 5] Suvorexant: 1H NMR (400 MHz, Chloroform-d) δ 7.90−7.75 (m, 3H), 7.68-7.01 (m, 5H), 5.09 – 4.46 (m, 1H), 4.23 – 3.41 (m, 6H), 3.16-2.31 (m, 4H), 2.20 – 2.01 (m, 1H), 1.91 – 1.16 (m, 3H); [4, 5]
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suvorexant
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