Photocatalytic Oxidative C–H Thiolation: Synthesis of Benzothiazoles and Sulfenylated Indoles

Andrew N. Dinh; Ashley D. Nguyen; Ernesto Millan Aceves; Samuel T. Albright; Mario R. Cedano; Diane K. Smith; Jeffrey L. Gustafson

doi:10.1055/s-0039-1690107

Synlett, Inhaltsverzeichnis

Synlett 2019; 30(14): 1648-1655
DOI: 10.1055/s-0039-1690107

cluster

Photocatalytic Oxidative C–H Thiolation: Synthesis of Benzothiazoles and Sulfenylated Indoles

Andrew N. Dinh ‡

,

Ashley D. Nguyen ‡

,

Ernesto Millan Aceves

,

Samuel T. Albright

,

Mario R. Cedano

,

Diane K. Smith

,

Jeffrey L. Gustafson∗

Abstract

Alle Artikel dieser Rubrik

^‡ Both authors contributed equally

Published as part of the Cluster for Organosulfur and Organoselenium Compounds in Catalysis

Abstract

We report studies on the photocatalytic formation of C–S bonds to form benzothiazoles via an intramolecular cyclization and sulfenylated indoles via an intermolecular reaction. Cyclic voltammetry (CV) and density functional theory studies suggest that benzothiazole formation proceeds via a mechanism that involves an electrophilic sulfur radical, while the indole sulfenylation likely proceeds via a nucleophilic sulfur radical adding into a radical cationic indole. These conditions were successfully extended to several thiobenzamides and indole substrates.

Key words

photoredox catalysis - benzothiazole - indole - thiolation - C–H functionalization

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Referenzen

References and Notes
1 Dunbar KL, Scharf DH, Litomska A, Hertweck C. Chem. Rev. 2017; 117: 5521
2 Johannesson P, Lindeberg G, Johansson A, Nikiforovich GV, Gogoll A, Synnergren B, Gre ML, Nyberg F, Karlen A, Hallberg A. J. Med. Chem. 2002; 45: 1767
3 Kazemi M, Shiri L, Kohzadi H, Kazemi M, Shiri L, Kohzadi H. Phosphorus, Sulfur, Silicon Relat. Elem. 2015; 190: 978
4 Marcantoni E, Massaccesi M, Petrini M, Bartoli G, Bellucci MC, Bosco M, Sambri L. J. Org. Chem. 2000; 65: 4553
5 Vazquez-Prieto MA, Miatello RM. Mol. Aspects Med. 2010; 31: 540
6 Vouillamoz J, Entenza M, Hohl P, Moreillon P. Antimicrob Agents Chemother 2004; 48: 4322
7 Takimiya K, Osaka I, Mori T, Nakano M. Acc. Chem. Res. 2014; 47: 1493
8 Gill R, Rawal R, Bariwal J. Arch. Pharm. Chem. Life Sci. 2015; 348: 155
9 Lee C, Liu Y, Badsara SS. Chem. Asian J. 2014; 9: 706
10 Beletskaya IP, Ananikov VP. Chem. Rev. 2011; 111: 1596
11 Vásquez-Céspedes S, Ferry A, Candish L, Glorius F. Angew. Chem. Int. Ed. 2015; 54: 5772
12 Stavber S. Molecules 2011; 16: 6432
13 Schlosser KM, Krasutsky AP, Hamilton HW, Reed JE, Sexton K. Org. Lett. 2004; 6: 819
14 Tudge M, Tamiya M, Savarin C, Humphrey GR. Org. Lett. 2006; 8: 565
15 Gillis M, Greene L, Thompson A. Synlett 2009; 112
16 Matsugi M, Murata K, Nambu H, Kita Y. Tetrahedron 2001; 42: 1077
17 Nalbandian CJ, Brown ZE, Alvarez E, Gustafson JL. Org. Lett. 2018; 20: 3211
18 Nalbandian CJ, Miller EM, Toenjes ST, Gustafson JL. Chem. Commun. 2017; 53: 1494
19 Prier CK, Rankic DA, Macmillan DW. C. Chem. Rev. 2013; 113: 5322
20 Romero NA, Nicewicz DA. Chem. Rev. 2016; 116: 10075
21 Wang C, Dixneuf P, Soule J.-F. Chem. Rev. 2018; 118: 7532
22 Shaw MH, Twilton J, Macmillan DW. C. J. Org. Chem. 2016; 81: 6898
23 Smith JM, Harwood SJ, Baran PS. Acc. Chem. Res. 2018; 51: 1807
24 Zhang G, Liu C, Yi H, Meng Q, Bian C, Chen H, Jian J, Wu L, Lei A. J. Am. Chem. Soc. 2015; 137: 9273
25 Qian X, Li S, Song J, Xu H. ACS Catal. 2017; 7: 2730
26 Rahaman R, Das S, Barman P. Green Chem. 2018; 20: 141
27 Guo W, Tan W, Zhao M, Tao K, Zheng L, Wu Y, Chen D, Fan X. RSC Adv. 2017; 7: 37739
28 Das A, Maity M, Malcherek S, König B, Rehbein J. Beilstein J. Org. Chem. 2018; 14: 2520
29 Zhang L, Hu X. Chem. Sci. 2017; 8: 7009
30 Rountree KJ, Mccarthy BD, Rountree ES, Eisenhart TT, Dempsey JL. J. Chem. Educ. 2017; 95: 197
31 Hua AM, Bidwell SL, Baker SI, Hratchian HP, Baxter RD. ACS Catal. 2019; 9: 3322
32 Cruz CL, Nicewicz DA. ACS Catal. 2019; 9: 3926
33 Morse PD, Nicewicz DA. Chem. Sci. 2015; 6: 270
34 Mcmanus JB, Nicewicz DA. J. Am. Chem. Soc. 2017; 139: 2880
35 Denes F, Pichowicz M, Povie G, Renaud P. Chem. Rev. 2014; 114: 2587
36 General Procedure for Synthesis of Substituted BenzothiazolesIn a 10 mL scintillation vial, thioabenzamide (1.0 equiv), Ru(bpy)₃Cl₂ (5 mol%), Na₂S₂O₈ (2.0 equiv), and pyridine (2.0 equiv) were added to a solution of 1:1 MeCN/H₂O (25 mg/1 mL). The reaction was stirred under blue LEDs for 12 h at room temperature. The resulting solution was quenched with H₂O, extracted with EtOAc, dried over Na₂SO₄, and concentrated in vacuo. The product was purified via FCC and prep TLC with gradient from hexanes to 8:2 Hex/EtOAc.General Procedure for the Synthesis of Sulfenylated IndolesIn a 10 mL scintillation vial, substituted indole (1.0 equiv), {Ir[dF(CF₃)ppy]₂(dtbpy)}PF₆ photocatalyst (1 mol%), Na₂S₂O₈ (2.0 equiv), KOH (2.0 equiv), and thiophenol (1.2 equiv) were added to a solution of 1:1 MeCN/H₂O (25 mg/1 mL). The reaction was left to stir under blue LEDs for 12 h at room temperature. The resulting solution was quenched with H₂O and extracted with EtOAc, dried over Na₂SO₄, and concentrated in vacuo. The product was purified via FCC and prep TLC (8:2 Hex/EtOAc). Melatonin substrates were purified via FCC with (2:8 Hex/EtOAc).2-(tert-Butyl)benzo[d]thiazole (1b)57% with no pyridine, 79% with pyridine, off-white solid. ¹H NMR (500 MHz, CDCl₃): δ = 8.00 (dt, J = 8.2, 0.9 Hz, 1 H), 7.85 (dd, J = 8.0, 0.45 Hz, 1 H), 7.44 (ddd, J = 8.3, 7.2, 1.3 Hz, 1 H), 7.34 (ddd, J = 8.2, 7.2, 1.2 Hz, 1 H), 1.53 (s, 9 H). The spectral data are in agreement with the reported literature.³⁷ MS-APCI: m/z calcd: C₁₁H₁₃NS [M + H]⁺ 192.3; found: 192.1.2-(tert-Butyl)napthol[1,2-d]thiazole (6b)55% with no pyridine, 54% with pyridine, yellow-green solid. ¹H NMR (500 MHz, CDCl₃): δ = 8.82 (dt, J = 8.0, 0.8 Hz, 1 H), 7.93 (d, J = 8.1 Hz, 1 H), 7.87 (d, J = 8.7 Hz, 1 H), 7.75 (d, J = 8.7 Hz, 1 H), 7.65 (ddd, J = 8.2, 6.9, 1.3 Hz, 1 H), 7.55 (ddd, J = 8.2, 6.9, 1.3 Hz, 1 H), 1.59 (s, 9 H). ¹³C NMR (101 Hz, CDCl₃): δ = 180.7, 149.2, 131.8, 131.2, 128.6, 127.9, 126.6, 125.7, 125.0, 124.0, 119.0, 38.4, 31.0. MS-APCI: m/z calcd for C₁₅H₁₅NS [M+H]⁺: 242.4; found: 242.1. N-{2-[5-Methoxy-2-(p-tolylthio)-1H-indol-3- yl]ethyl}acetamide (18b)68%, tan solid. ¹H NMR (400 MHz, CDCl₃): δ = 8.12 (s, 1 H), 7.22 (d, 8.8 Hz, 1 H), 7.02–7.06 (m, 3 H), 6.98 (d, 8.3 Hz, 2 H), 6.91 (dd, J = 8.8, 2.4 Hz, 1 H), 5.50 (s, 1 H), 3.86 (s, 3 H), 3.52 (q, J = 6.4 Hz, 2 H), 3.05 (t, J = 6.5 Hz, 2 H), 2.27 (s, 3 H), 1.78 (s, 3 H). ¹³C NMR (126 Hz, CDCl₃): δ = 170.28, 154.36, 136.17, 133.22, 132.07, 130.04, 128.13, 127.00, 123.50, 119.64, 114.32, 111.93, 100.32, 55.87, 40.01, 24.75, 23.13, 20.89. MS-APCI: m/z calcd for C₂₀H₂₂N₂O₂S [M + H]⁺: 355.5; found: 355.5
37 Zhang G, Liu C, Yi H, Meng Q, Bian C, Chen H, Jian JX, Wu LZ, Lei A. J. Am. Chem. Soc. 2015; 137: 9273

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