A Convenient Method to Aniline Compounds Using Microwave-Assisted Transfer Hydrogenation

Abstract

The reduction of mononitro and dinitro aromatic compounds to their aniline analogues using microwave-assisted transfer hydrogenation has been demonstrated. The optimised conditions used, with some examples, are described herein.

Key words

microwave - transfer hydrogenation - nitroaromatic - anilines

References and Notes

• 1 Knifton JF. J. Org. Chem.  1976,  41:  1200 
• 2a Onopchenko A. Sabourin ET. Selwitz CM. J. Org. Chem.  1979,  44:  1233 
• 2b Knifton JF. Tetrahedron Lett.  1975,  26:  2163 
• 3 Love C. McQuillin FJ. J. Chem. Soc., Perkin Trans. 1  1973,  2509 
• 4 Onopchenko A. Sabourin ET. Selwitz CM. J. Org. Chem.  1979,  44:  1233 
• 5a Secrist JA. Logue MW. J. Org. Chem.  1972,  37:  335 
• 5b Rogers ME. Averill BA. J. Org. Chem.  1986,  51:  3308 
• 5c Nakano M. Sato Y. J. Org. Chem.  1987,  52:  1844 
• 5d Lee M. Lown JW. J. Org. Chem.  1987,  52:  5717 
• 5e Manabe K. Okamura K. Date T. Koga K. J. Org. Chem.  1993,  58:  6692 
• 5f Sleath PR. Noar JB. Eberlein GA. Bruice TC. J. Am. Chem. Soc.  1985,  107:  3328 
• 5g Evans DA. Miller SJ. Ennis MD. J. Org. Chem.  1993,  58:  471 
• 5h Mukkanti K. Subba Rao YV. Choudary BM. Tetrahedron Lett.  1989,  30:  251 
• 6a Adams R. Cohen FL. Org. Synth. Coll. Vol. I  1941,  240 
• 6b Skiles JW. Cava MP. J. Org. Chem.  1979,  44:  409 
• 6c Wetherill RB. Brown HC. Sivasankaran K. J. Am. Chem. Soc.  1962,  84:  2828 
• 7a Natelson S. Gottfried SP. J. Am. Chem. Soc.  1939,  61:  1001 
• 7b Sheehan M. Cram DJ. J. Am. Chem. Soc.  1969,  91:  3544 
• 7c Doxsee KM. Feigel M. Stewart KD. Canary JW. Knobler CB. Cram DJ. J. Am. Chem. Soc.  1987,  109:  3098 
• 7d Schiemann G. Pillarsky R. Chem. Ber.  1929,  62:  3035 
• 8a Wentland MP. Kullnig RK. Tham FS. J. Org. Chem.  1991,  56:  4706 
• 8b Mahood SA. Schaffner PVL. Org. Synth,. Coll. Vol. II  1943,  160 
• 8c Fox BA. Threlfall TL. Org. Synth., Coll. Vol. V  1973,  346 
• 9 Subba Rao NV. Ratnam CV. Proc. Indian Acad. Sci., Sect. A  1956,  44:  331 
• 10a Linstead RP. Braude EA. Wooldridge KRH. J. Chem. Soc.  1954,  3586 
• 10b Entwistle ID. Johnstone RAW. Povall TJ. J. Chem. Soc., Perkin Trans. 1  1975,  1300 
• 10c Yeh M. Tang F. Chen S. Liu W. Lin L. J. Org. Chem.  1994,  59:  754 
• 11a Frisch KC. Taylor Bogert M. J. Org. Chem.  1943,  8:  331 
• 11b Lyli RE. Lamattina JL. Synthesis  1974,  726 
• 11c Theodoridis G. Manfredi MC. Krebs JD. Tetrahedron Lett.  1990,  31:  6141 
• 12a Wong JC. Wen-Ben Y. Chung-Ming S. Synlett  2003,  1688 
• 12b Bendale PM. Chung-Ming S. J. Comb. Chem.  2002,  4:  359 
• 12c Kamal A. Srinivasa Reddy K. Rajendra Prasad B. Hari Babu A. Venkata Ramana A. Tetrahedron Lett.  2004,  45:  6517 
• 13 Ravi Kanth S. Venkat Reddy G. Rama Rao VVVNS. Maitraie D. Narsaiah B. Shanthan Rao P. Synth. Commun.  2002,  32:  2849 
• 14 Lidstrom P. Tierney J. Wathey B. Westman J. Tetrahedron  2001,  57:  9225 

15

Each isomer was separated and characterised by ¹H NMR and ¹³C NMR spectroscopy. For each isomer, an NOE was observed between the NH₂ and the aromatic proton.

16

The conversion of 2-[(E)-2-(4-pyridinyl)ethenyl]aniline to the 2-[2-(4-pyridinyl)ethyl]aniline required microwave conditions of 180 °C, 120 min in EtOH.

17

3-(Ethyloxy)-4-nitroaniline. Synthesised using heating time of 3 min. ¹H NMR [400 MHz, (CD₃)₂SO]: δ = 1.35 (t, J = 8 Hz, 3 H, CH₃), 4.05 (q, J = 8 Hz, 2 H, CH₂), 6.18 (d, J = 8 Hz, 1 H, ArH), 6.24 (s, 1 H, ArH), 6.53 (br s, 2 H, NH₂), 7.78 (d, J = 8 Hz, 1 H, ArH), 7.71 (d, J = 8 Hz, ArH). ¹³C NMR [75 MHz, (CD₃)₂SO]: δ = 14.8, 64.5, 96.9, 105.9, 127.2, 129.3, 156.3, 156.5. MS (EI, 70 eV): m/z (%) = 182.97 (100). HRMS-FAB: m/z calcd for C₈H₁₀N₂O₃ [M + H]⁺: 183.0770; found: 183.0775.
2-(Ethyloxy)-4-nitroaniline.
Synthesised using heating time of 3 min. ¹H NMR [400 MHz, (CD₃)₂SO]: δ = 1.37 (t, J = 8 Hz, 3 H, CH₃), 4.10 (q, J = 8 Hz, 2 H, CH₂), 6.40 (br s, 2H, NH₂), 6.64 (d, J = 8 Hz, 1 H, ArH), 7.54 (s, 1 H, ArH), 7.71 (d, J = 8 Hz, ArH). ¹³C NMR [75 MHz, (CD₃)₂SO]: δ = 14.5, 63.9, 106.3, 110.8, 119.6, 135.4, 143.6, 146.1. MS (EI, 70 eV): m/z (%) = 182.85 (100). HRMS-FAB: m/z calcd for C₈H₁₀N₂O₃ [M + H]⁺: 183.0770; found: 183.0775.
2-[( E )-2-(4-pyridinyl)ethenyl]aniline.
Synthesised using heating time of 90 min. ¹H NMR [400 MHz, (CD₃)₂SO]: δ = 5.51 (s, 2 H, NH₂), 6.55 (t, J = 4 Hz, 1 H, ArH), 6.65 (d, J = 8 Hz, 1 H, ArH), 6.96 (d, J = 16 Hz, 1 H, CH), 7.01 (m, 1 H, ArH), 7.47 (d, J = 8 Hz, 1 H, ArH), 7.57 (br d, J = 4 Hz, 2 H, ArH), 7.67 (d, J = 16 Hz, 1 H, CH), 8.51 (br s, 2 H, ArH). ¹³C NMR (75 MHz, CDCl₃): δ = 115.7, 116.6, 119.4, 120.61, 123.7, 125.7, 128.8, 129.5, 145.1, 146.3, 149.2. MS (EI, 70 eV): m/z (%) = 197.0 (100). HRMS-FAB: m/z calcd for C₁₃H₁₃N₂ [M + H]⁺: 197.1083; found: 197.1079.
1 H -Indazol-6-amine Synthesised using heating time of 15 min. ¹H NMR [400 MHz, (CD₃)₂SO]: δ = 5.18 (s, 2 H, NH₂), 6.48 (dd, J = 8, 4 Hz, 1 H, ArH), 6.50 (s, 1 H, CH), 7.35 (d, J = 8 Hz, 1 H, ArH), 7.71 (s, 1 H, ArH) 12.3 (s, NH). ¹³C NMR (75 MHz, CDCl₃): δ = 89.6, 111.5, 114.7, 119.7, 132.3, 141.1, 146.8. MS (EI, 70 eV): m/z (%) = 134.02 [M + H]⁺ (100). HRMS-FAB: m/z calcd for C₇H₇N₃ [M + H]⁺: 134.0717; found: 134.0718.