Chemoselective Vicinal Dichlorination of Alkenes by Iron Ligand-to-Metal Charge-Transfer Catalysis

Abstract

We report the photocatalytic functionalization of terminal alkenes to vicinal dichlorides by using visible light and FeCl₃ as a catalyst, LiCl as a chloride source, and air as an oxidant. The transformation is proposed to be initiated by ligand-to-metal charge-transfer bond homolysis of a Fe–Cl bond, giving a highly reactive chloride radical able to initiate the functionalization of olefins. The process shows high chemoselectivity and broad functional-group tolerance with yields of up to 94% under mild conditions.

Key words

iron catalysis - photocatalysis - ligand-to-metal charge transfer - chlorination - alkenes - vicinal dichlorides

Publikationsverlauf

Eingereicht: 26. Oktober 2023

Angenommen nach Revision: 11. Dezember 2023

Accepted Manuscript online:
11. Dezember 2023

Artikel online veröffentlicht:
18. Januar 2024

• References and Notes

• 1 Fauvarque J. Pure Appl. Chem. 1996; 68: 1713
• 2 Baldwin RT. J. Chem. Educ. 1927; 4: 313
• 3 Rajkumar D, Kim JG. J. Hazard. Mater. 2006; 136: 203
• 4 Morosin B. J. Chem. Phys. 1968; 49: 3007
• 5 Recio JM, Pendás AM, Francisco E, Flórez M, Luaña V. Phys. Rev. B 1993; 48: 5891
• 6 Dreher E.-L, Torkelson TL, Beutel KK, Myers JD, Lübbe T, Kreiger S, Pottenger LH. In Ullmann’s Encyclopedia of Industrial Chemistry . Wiley-VCH; Weinheim: 2014.
• 7 Achanta S, Jordt S.-E. Toxicol. Mech. Methods 2021; 31: 244
• 8 Lian P, Long W, Li J, Zheng Y, Wan X. Angew. Chem. Int. Ed. 2020; 59: 23603
• 9 Kochi JK. J. Am. Chem. Soc. 1962; 84: 2121
• 10 Feng G, Wang X, Jin J. Eur. J. Org. Chem. 2019; 6728
• 11 Chen J, Browne WR. Coord. Chem. Rev. 2018; 374: 15
• 12 Wedepohl KH. In Elements and Their Compounds in the Environment: Occurrence, Analysis and Biological Relevance, 2nd ed., Vol. 1, Chap. 1. Merian E, Anke M, Ihnat M, Stoeppler M. Wiley-VCH; Weinheim: 2004: 2
• 13 Fürstner A. ACS Cent. Sci. 2016; 2: 778
• 14 Vogler A, Kunkely H. Coord. Chem. Rev. 2000; 208: 321
• 15 Inoue H, Tamaki K, Komakine N, Imoto E. Bull. Chem. Soc. Jpn. 1967; 40: 875
• 16 Wang X, Shi C, Yang M, Ma Y, Chen Y, Lu T, Tang W, Feng J. Asian J. Org. Chem. 2023; 12: e202300077
• 17 Treacy SM, Rovis T. J. Am. Chem. Soc. 2021; 143: 2729
• 18 Ding L, Niu K, Liu Y, Wang Q. ChemSusChem 2022; 15: e202200367
• 19 Fleischmann S, Percec V. J. Polym. Sci., Part A: Polym. Chem. 2010; 48: 4889
• 20 Dey D, Patra M, Al-Hunaiti A, Yadav HR, Al-mherat A, Arar S, Maji M, Choudhury AR, Biswas B. J. Mol. Struct. 2019; 1180: 220
• 21 Bian K.-J, Kao S.-C, Nemoto D, Chen X.-W, West JG. Nat. Commun. 2022; 13: 7881
• 22 Preparative-Scale Iron-Catalyzed Dichlorination of Alkenes; General Procedure After successful screening at a 0.1 mmol scale, the preparative-scale reactions were performed in 6–12 parallel vials to achieve good reproducibility. Each vial was equipped with a magnetic stirrer bar and charged the appropriate alkene ester starting material (0.20 mmol, 1.00 equiv), FeCl₃ (0.04 mmol, 6.50 mg, 20.0 mol%), and LiCl (2.00 mmol, 85.0 mg, 10.0 equiv) in 9:1 AcOH–MeCN (0.5 mL). The glass vials were closed, and air was added by syringe through a semi-permeable septum in the cap of each vial. The vials were sealed with Parafilm and placed in the thermostatted (20 °C) metal block approximately 2 cm above the 390–395 nm light source, and the mixtures were irradiated for 3 h. The vials were then opened to air and their contents were combined, filtered through a thin layer of silica gel in a vacuum filtration device, washed with Et₂O, and collected in a 100 mL round-bottomed flask. The solvent volume was reduced under reduced pressure and the residue was extracted with H₂O (2 × 20 mL) and NaHCO₃ (20 mL). The combined organic layers were dried (Na₂SO₄), filtered, and then concentrated in vacuum. The oily residue was dried under reduced pressure and purified by flash column chromatography (silica gel, 20% acetone–PE). The purity of the product was confirmed by ¹H and ¹³C NMR analyses in CDCl₃ with triphenylmethane as a standard. 3,4-Dichlorobutyl Benzoate (1a) Colorless oil; yield: 0.023 g (47%, 0.093 mmol). ¹H NMR (300 MHz, CDCl₃): δ = 8.12–7.99 (m, 2 H), 7.62–7.49 (m, 1 H), 7.47–7.35 (m, 2 H), 4.62–4.41 (m, 2 H), 4.26 (dddd, J = 9.5, 7.3, 5.0, 3.5 Hz, 1 H), 3.83 (dd, J = 11.4, 5.0 Hz, 1 H), 3.72 (dd, J = 11.4, 7.3 Hz, 1 H), 2.50 (dddd, J = 14.5, 8.9, 5.8, 3.4 Hz, 1 H), 2.11 (ddt, J = 14.6, 9.7, 4.9 Hz, 1 H). ¹³C NMR (75 MHz, CDCl₃): δ = 166.3 (Cq), 133.2 (+), 129.9 (Cq), 129.6 (+), 128.5 (+), 61.4 (–), 57.6 (+), 48.3 (–), 34.3 (–). The spectroscopic results agreed well with those in the literature; see ref. 8.
• 23 Lynn E, Kobe AK. Ind. eng. chem. 1954; 46: 633
• 24 Sun X, Liu X, Qin Y, He Y, Su D, Song Li, Su Z. Ind. Eng. Chem. Res. 2019; 58: 5404