Photoinduced Reduction of Nitrobenzenes to Primary Aromatic Amines

Abstract

Primary aromatic amines were synthesized from the corresponding nitrobenzenes via photoinduced reduction. The reaction was found to be effective when nitrobenzenes with electron-withdrawing substituents were irradiated with a broad band of UV light centered at 306 nm. When reactions are completed, products could be isolated by acid–base extraction or by column chromatography. This presenting photoreaction procedure for the synthesis of primary aromatic amines from the corresponding nitrobenzenes proceeds without the need of a sensitizer in isopropanol or THF. Without the usage of catalysts, or stoichiometric reducing reagent containing heavy metals, this photoinduced reduction of nitrobenzenes fulfils the concept of green chemistry.

Key words

photoreaction - reduction - anilines - nitrobenzenes - UV light

• References and Notes

• 1 Kim EJ, Matuszek AM, Yu B, Reynisson J. Aust. J. Chem. 2011; 64: 910-910
• 2a Rangappa K, Chandrappa S, Vinaya K, Ramakrishnappa T. Synlett 2010; 3019-3019
• 2b Mortensen SK, Trier XT, Foverskov A, Petersen JH. J. Chromatogr. A 2005; 1091: 40-40
• 2c Pinheiro HM, Touraud E, Thomas O. Dyes Pigm. 2004; 61: 121-121
• 3a Wang L, Li P, Wu Z, Yan J, Wang M, Ding Y. Synthesis 2003; 2001-2001
• 3b Herepoulos GA, Georgakopoulos S, Steele BR. Tetrahedron Lett. 2005; 46: 2469-2469
• 4a Nagaraja D, Pasha MA. Tetrahedron Lett. 1999; 40: 7855-7855
• 4b Pyo SH, Han BH. Bull. Korean Chem. Soc. 1995; 16: 81-81
• 5a Zinin N. Adv. Synth. Catal. 1842; 27: 140-140
• 5b Zimmermann V, Avemaria F, Bräse S. J. Comb. Chem. 2007; 9: 200-200
• 6 Barltrop JA, Bunce NJ. J. Chem. Soc. C 1968; 1467-1467
• 7 Cors A, Bonesi SM, Erra-Balsells R. Tetrahedron Lett. 2008; 49: 1555-1555

Selected references of the challenge in the selective reduction of dinitrobenzene to the 4-nitroaniline:
• 8a Chen Y, Qiu J, Wang X, Xiu J. J. Catal. 2006; 242: 227-227
• 8b Gowda DC, Mahesh B, Gowda S. Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem. 2001; 40: 75-75
• 8c Pogorelić I, Filipan-Litvić M, Merkaš S, Ljubić G, Cepanec I, Litvić M. J. Mol. Catal. A: Chem. 2007; 274: 202-202
• 8d Zand Z, Kazemi F, Hosseini S. Tetrahedron Lett. 2014; 55: 338-338
• 9a Chen Y, Qiu J, Wang X, Xiu J. J. Catal. 2006; 242: 227-227
• 9b Gowda DC, Mahesh B, Gowda S. Indian J. Chem., Sect. B: Org. Chem. Incl. Med. Chem. 2001; 40: 75-75
• 9c Pogorelić I, Filipan-Litvić M, Merkaš S, Ljubić G, Cepanec I, Litvić M. J. Mol. Catal. A: Chem. 2007; 274: 202-202
• 9d Zand Z, Kazemi F, Hosseini S. Tetrahedron Lett. 2014; 55: 338-338
• 10 General Procedure I for the Photoinduced Reduction in i-PrOH Nitroarene (20 mg) was added into 20 mL i-PrOH. The quartz tube containing the solution was degassed by ultrasonic cleaner for 1 h prior to use. The reaction was stirred at r.t. under UV irradiation (306 nm). Consumption of starting material was monitored by TLC. Solvent was removed under reduced pressure, and the crude mixture was transferred to a separatory funnel containing 1 M HCl. The aqueous layer was extracted two times with CH₂Cl₂. The aqueous layer was then basified using 1 N NaOH and extracted two times with EtOAc. The combined organic layers were washed with brine, dried (MgSO₄), and concentrated to provide the desired primary aromatic amines. 4-Aminobenzonitrile (2a) Following the General Procedure I, using 4-nitrobenzonitrile (20.0 mg, 0.135 mmol), provided the title compound as a yellowish powder (12 mg, 75% yield). ¹H NMR (300 MHz, CDCl₃, 24 °C ): δ = 7.41 (d, J = 8.6 Hz, 2 H), 6.64 (d, J = 8.7 Hz, 2 H), 4.11 (s, 2 H). The ¹H NMR spectroscopic data is consistent with the literature value.^12a
• 11 General Procedure II for the Photoinduced Reduction in THF Nitroarene (50 mg) was added into 25 mL THF. The quartz tube containing the solution was degassed by ultrasonic cleaner for 1 h prior to use. The reaction was stirred at r.t. under UV irradiation (306 nm). Consumption of starting material was monitored by TLC. The reaction mixture was transferred to a flask which was contained Al₂O₃ (5 g) and then reflux until the intermediate was consumed. Solvent was removed under reduced pressure, and the crude mixture was transferred to a separatory funnel containing 1 M HCl. The aqueous layer was extracted two times with CH₂Cl₂. The aqueous layer was then basified using 1 N NaOH and extracted two times with EtOAc. The combined organic layers were washed with brine, dried (MgSO₄), and concentrated to provide the desired primary aromatic amines. 3-Aminobenzonitrile (2b) Following the General Procedure II, using 3-nitrobenzonitrile (50.0 mg, 0.338 mmol), provided the title compound as a yellowish powder (27 mg, 66% yield). ¹H NMR (300 MHz, CDCl₃, 24 °C): δ = 7.22 (t, 1 H, J = 7.9 Hz), 7.02 (d, 1 H, J = 7.6 Hz), 6.90–6.85 (m, 2 H), 3.85 (s, 2 H). The ¹H NMR spectroscopic data is consistent with the literature value.^12b
• 12a Orlandi M, Tosi F, Bonsignore M, Benaglia M. Org. Lett. 2015; 17: 3941-3941
• 12b Papadas IT, Fountoulaki S, Lykakis IN, Armatas GS. Chem. Eur. J. 2016; 22: 4600-4600