Synlett
DOI: 10.1055/a-1956-9993
cluster
Special Issue Chemical Synthesis and Catalysis in India

Easy Access to N-(Pyridin-2-yl)benzamides through Electro-oxidative Ring Opening of 2-Arylimidazo[1,2-a]pyridines

Sayan Ghosh
,
Jhilik Dutta
,
Atreyee Halder
,
Generous supports by the Department of Science and Technology (DST), India (INSPIRE Fellowship to SG), the Science and Engineering Research Board (SERB), India (CRG/2020/006021 to S.D.S.), and Indian Institute of Science Education and Research (IISER) Kolkata (Fellowship to J.D., A.H., and infrastructure) are gratefully acknowledged.


Abstract

An electro-oxidative method for the ring opening of imidazopyridine derivatives is reported. This mild protocol offers a sustainable alternative to the existing harsh reaction conditions and unleashes an efficient approach to produce N-(pyridin-2-yl)amide derivatives with good tolerance of different functional groups. Systematic mechanistic studies provided insight into the reaction pathway and revealed that the residual water of DMSO is the source of oxygen atoms in the products.

Supporting Information



Publication History

Received: 31 August 2022

Accepted after revision: 07 October 2022

Accepted Manuscript online:
07 October 2022

Article published online:
07 November 2022

© 2022. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 
  • References and Notes

    • 1a Drahl MA, Manpadi M, Williams LJ. Angew. Chem. Int. Ed. 2013; 52: 11222
    • 1b Song F, Gou T, Wang BQ, Shi ZJ. Chem. Soc. Rev. 2018; 47: 7078
    • 2a Chen F, Wang T, Jiao N. Chem. Rev. 2014; 114: 8613
    • 2b Sivaguru P, Wang Z, Zanoni G, Bi X. Chem. Soc. Rev. 2019; 48: 2615
    • 2c Vicente R. Chem. Rev. 2021; 121: 162
    • 3a Chattopadhyay B, Gevorgyan V. Angew. Chem. Int. Ed. 2012; 51: 862
    • 3b Yorimitsu H, Vasu D, Bhanuchandra M, Murakami K, Osuka A. Synlett 2016; 27: 1765
    • 3c Saito H, Yorimitsu H. Chem. Lett. 2019; 48: 1019
    • 3d Xuan J, He XK, Xiao WJ. Chem. Soc. Rev. 2020; 49: 2546
  • 4 Volpi G, Rabezzana R. New J. Chem. 2021; 45: 5737
    • 5a Guo Y.-J, Lu S, Tian L.-L, Huang E.-L, Hao X.-Q, Zhu X, Shao T, Song M.-P. J. Org. Chem. 2017; 83: 338
    • 5b Mondal S, Samanta S, Jana S, Hajra A. J. Org. Chem. 2017; 82: 4504
    • 5c Iida H, Demizu R, Ohkado R. J. Org. Chem. 2018; 83: 12291
    • 5d Jana S, Samanta S, Bagdi AK, Shirinian VZ, Hajra A. RSC Adv. 2018; 8: 12360

    • Reviews:
    • 5e Tashrifi Z, Mohammadi-Khanaposhtani M, Larijani B, Mahdavi M. Eur. J. Org. Chem. 2020; 269
    • 5f Ramana Reddy M, Darapaneni CM, Patil RD, Kumari H. Org. Biomol. Chem. 2022; 20: 3440
  • 6 Wang R, Wang S, Li D, Ye F, Leng Y, Wu Y, Chang J, Wu Y. Tetrahedron 2019; 75: 2298
  • 7 Yan K, Yang D, Wei W, Li G, Sun M, Zhang Q, Tian L, Wang H. RSC Adv. 2015; 5: 100102
  • 8 Liu Y, Lu L, Zhou H, Xu F, Ma C, Huang Z, Xu J, Xu S. RSC Adv. 2019; 9: 34671
  • 9 Ritu, Sharma C, Kumar S, Jain N. Org. Biomol. Chem. 2020; 18: 2921
    • 10a Liu Y, Sun H, Huang Z, Ma C, Lin A, Yao H, Xu J, Xu S. J. Org. Chem. 2018; 83: 14307
    • 10b Zhou H, Liu Y, Xia H, Xu J, Wang T, Xu S. Eur. J. Org. Chem. 2020; 6468
    • 11a Alam T, Rakshit A, Dhara HN, Palai A, Patel BK. Org. Lett. 2022; 24: 6619 Reviews
    • 11b Francke R, Little RD. Chem. Soc. Rev. 2014; 43: 2492
    • 11c Wiebe A, Gieshoff T, Mohle S, Rodrigo E, Zirbes M, Waldvogel SR. Angew. Chem. Int. Ed. 2018; 57: 5594
    • 11d Wang H, Gao X, Lv Z, Abdelilah T, Lei A. Chem. Rev. 2019; 119: 6769
    • 11e Pollok D, Waldvogel SR. Chem. Sci. 2020; 11: 12386
    • 11f Zhu C, Ang NW. J, Meyer TH, Qiu Y, Ackermann L. ACS Cent. Sci. 2021; 7: 415
    • 11g Tay NE. S, Lehnherr D, Rovis T. Chem. Rev. 2022; 122: 2487
    • 12a Yan M, Kawamata Y, Baran PS. Chem. Rev. 2017; 117: 13230
    • 12b Liu J, Lu L, Wood D, Lin S. ACS Cent. Sci. 2020; 6: 1317
    • 12c Wang F, Stahl SS. Acc. Chem. Res. 2020; 53: 561
    • 12d Wu T, Moeller KD. Angew. Chem. Int. Ed. 2021; 60: 12883
    • 13a Gao Y, Wang Y, Zhou J, Mei H, Han J. Green Chem. 2018; 20: 583
    • 13b Yu Y, Yuan Y, Liu H, He M, Yang M, Liu P, Yu B, Dong X, Lei A. Chem. Commun. 2019; 55: 1809
    • 13c Park JW, Kim YH, Kim DY. Synth. Commun. 2020; 50: 710
    • 13d Meng ZY, Feng CT, Zhang L, Yang Q, Chen DX, Xu K. Org. Lett. 2021; 23: 4214
  • 14 Ghosh D, Ghosh S, Hajra A. Adv. Synth. Catal. 2021; 363: 5047
    • 15a Azizollahi H, García-López JA. Molecules 2020; 25: 5900
    • 15b Shi SH, Liang Y, Jiao N. Chem. Rev. 2021; 121: 485
    • 15c Adeli Y, Huang K, Liang Y, Jiang Y, Liu J, Song S, Zeng C.-C, Jiao N. ACS Catal. 2019; 9: 2063
    • 15d Peng P, Yan X, Zhang K, Liu Z, Zeng L, Chen Y, Zhang H, Lei A. Nat. Commun. 2021; 12: 3075
    • 15e Liao LL, Wang ZH, Cao KG, Sun GQ, Zhang W, Ran CK, Li Y, Chen L, Cao GM, Yu DG. J. Am. Chem. Soc. 2022; 144: 2062
    • 15f Shen T, Liu S, Zhao J, Wang N, Yang L, Wu J, Shen X, Liu ZQ. J. Org. Chem. 2022; 87: 3286
    • 15g Wang R, Sun P, Jin W, Zhang Y, Wang B, Xia Y, Xue F, Abdukader A, Liu C. Org. Chem. Front. 2022; 9: 2664
    • 16a Qin H, Yang Z, Zhang Z, Liu C, He W, Fang Z, Guo K. Chem. Eur. J. 2021; 27: 13024
    • 16b Wu J, Peng Z, Shen T, Liu ZQ. Adv. Synth. Catal. 2022; 364: 2565
    • 17a Maiti D, Halder A, Sasidharan Pillai A, De Sarkar S. J. Org. Chem. 2021; 86: 16084
    • 17b Maiti D, Mahanty K, De Sarkar S. Org. Lett. 2021; 23: 1742
    • 17c Baidya M, Maiti D, Roy L, De Sarkar S. Angew. Chem. Int. Ed. 2022; 61: e202111679
    • 17d Baidya M, Mallick S, De Sarkar S. Org. Lett. 2022; 24: 1274
  • 18 General Procedure (GP) for Electro-oxidative Ring-Opening2-Arylimidazo[1,2-a]pyridines 1 (0.25 mmol, 1.0 equiv), HClO4 (25 μmol, 10 mol%), and lithium perchlorate (53 mg, 0.1 M) were taken in an oven-dried undivided cell and dissolved in 5 mL of DMSO solvent. Thereafter graphite (3.0 cm × 0.8 cm × 0.2 cm) and platinum plate (3.0 cm × 0.8 cm × 0.025 cm) electrodes were dipped into the reaction mixture and connected with an AXIOMET AX-3003P power supply. The electrolysis was conducted along with continuous stirring for 2.5 h at 10 mA of constant current under air atmosphere at room temperature. After electrolysis, the reaction mixture was diluted with water and extracted with ethyl acetate (3 × 10 mL). The combined organic layer was dried with Na2SO4 and evaporated under reduced pressure. Purification of the product by column chromatography using 8–24% ethyl acetate in hexane yielded N-(pyridin-2-yl)benzamide derivatives 2.Analytical Data
    N-(Pyridin-2-yl)benzamide (2a)
    The GP was followed using 2-phenylimidazo[1,2-a]pyridine (1a, 48 mg, 0.25 mmol), HClO4 (1.5 μL, 10 mol%). After 2.5 h, purification by column chromatography in silica gel (100–200 mesh) using 10% ethyl acetate in hexane yielded 2a (40 mg, 80%) as a white solid. 1H NMR (500 MHz, CDCl3): δ = 9.60 (br, 1 H), 8.43 (d, J = 8.4 Hz, 1 H), 8.11 (d, J = 8.3 Hz, 1 H), 7.95 (d, J = 7.6 Hz, 2 H), 7.73 (t, J = 7.9 Hz, 1 H), 7.53 (t, J = 7.3 Hz, 1 H), 7.44 (t, J = 7.6 Hz, 2 H), 7.00 (t, J = 5.7 Hz, 1 H). 13C NMR{1H} (126 MHz, CDCl3): δ = 166.0, 151.2, 147.6, 139.0, 134.3, 132.4, 129.0, 127.5, 120.1, 114.6.4-Methyl-N-(pyridin-2-yl)benzamide (2b)The GP was followed using 2-(p-tolyl)imidazo[1,2-a]pyridine (1b, 52 mg, 0.25 mmol), HClO4 (1.5 μL, 10 mol%). After 2.5 h, purification by column chromatography in silica gel (100–200 mesh) using 8% ethyl acetate in hexane yielded 2b (36 mg, 68%) as a white solid. 1H NMR (500 MHz, CDCl3): δ = 8.75 (br, 1 H), 8.36 (d, J = 8.4 Hz, 1 H), 8.24 (d, J = 4.4 Hz, 1 H), 7.80 (d, J = 8.1 Hz, 2 H), 7.75–7.70 (m, 1 H), 7.26 (d, J = 7.9 Hz, 2 H), 7.05–7.01 (m, 1 H), 2.39 (s, 3 H). 13C NMR{1H} (126 MHz, CDCl3): δ = 165.8, 151.8, 147.8, 143.0, 138.7, 131.5, 129.6, 127.4, 119.9, 114.4, 21.7.4-Methoxy-N-(pyridin-2-yl)benzamide (2c)The GP was followed using 2-(4-methoxyphenyl)imidazo[1,2-a]pyridine (1c, 56 mg, 0.25 mmol), HClO4 (1.5 μL, 10 mol%). After 2.5 h, purification by column chromatography in silica gel (100–200 mesh) using 20% ethyl acetate in hexane yielded 2c (42 mg, 73%) as an off-white solid. 1H NMR (500 MHz, CDCl3): δ = 9.13 (br, 1 H), 8.41 (d, J = 8.4 Hz, 1 H), 8.29–8.23 (m, 1 H), 7.95 (d, J = 8.8 Hz, 2 H), 7.76 (t, J = 8.8 Hz, 1 H), 7.10–7.03 (m, 1 H), 6.98 (d, J = 8.8 Hz, 2 H), 3.87 (s, 3 H). 13C NMR{1H} (126 MHz, CDCl3): δ = 165.6, 163.0, 152.0, 147.5, 138.9, 129.5, 126.5, 119.8, 114.6, 114.1, 55.6. N-[5-(4-Methoxyphenyl)pyridin-2-yl]benzamide (2p)The GP was followed using 6-(4-methoxyphenyl)-2-phenylimidazo[1,2-a]pyridine (1p, 75 mg, 0.25 mmol), HClO4 (1.5 μL, 10 mol%). After 2.5 h, purification by column chromatography in silica gel (100–200 mesh) using 22% ethyl acetate in hexane yielded 2p (44 mg, 59%) as a white solid. 1H NMR (500 MHz, CDCl3): δ = 8.75 (br, 1 H), 8.48–8.44 (m, 2 H), 7.97–7.91 (m, 3 H), 7.61–7.45 (m, 5 H), 7.01 (d, J = 8.7 Hz, 2 H), 3.86 (s, 3 H). 13C NMR{1H} (126 MHz, CDCl3): δ = 165.7, 159.8, 150.3, 145.7, 136.6, 134.4, 133.0, 132.4, 130.0, 129.0, 128.0, 127.4, 114.73, 114.1, 55.6. N-(5-Cyanopyridin-2-yl)benzamide (2q)
    The GP was followed using 2-phenylimidazo[1,2-a]pyridine-6-carbonitrile (1q, 54 mg, 0.25 mmol), HClO4 (1.5 μL, 10 mol%). After 3.5 h, purification by column chromatography in silica gel (100–200 mesh) using 12% ethyl acetate in hexane yielded 2q (40 mg, 72%) as a white solid. 1H NMR (500 MHz, CDCl3): δ = 9.05 (s, 1 H), 8.60–8.54 (m, 2 H), 8.01 (dd, J = 8.8, 2.3 Hz, 1 H), 8.01–7.90 (m, 2 H), 7.66–7.57 (m, 1 H), 7.54 (dd, J = 8.4, 7.0 Hz, 2 H). 13C NMR{1H} (126 MHz, CDCl3): δ = 166.0, 154.3, 151.7, 141.9, 133.5, 133.1, 129.2, 127.6, 116.8, 114.0, 105.4.