InCl3-Catalyzed Alkylation of Aromatic and Heteroaromatic Compounds with Cyclic Allylic Acetates

J. S. Yadav; B. V. Subba Reddy; K. Vishweshwar Rao; P. Purushothama Rao; K. Sarita Raj; A. R. Prasad; A. Prabhakar; B. Jagadeesh

doi:10.1055/s-2006-958418

LETTER

InCl₃-Catalyzed Alkylation of Aromatic and Heteroaromatic Compounds with Cyclic Allylic Acetates

J. S. Yadav*^a, B. V. Subba Reddy^a, K. Vishweshwar Rao^a, P. Purushothama Rao^a, K. Sarita Raj^a, A. R. Prasad^a, A. Prabhakar^b, B. Jagadeesh^b
^a Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500007, India
Fax: +91(40)27160512; e-Mail: yadavpub@iict.res.in;
^b Centre for Nuclear Magnetic Resonance, Indian Institute of Chemical Technology, Hyderabad 500007, India

Abstract

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Abstract

Various aromatic and heteroaromatic compounds undergo smooth alkylation with cyclic allylic acetates in the presence of 10 mol% of indium trichloride under mild conditions to afford 3-substituted indoles, 2-substituted furan and pyrrole and cyclohexenyl-substituted arenes in good yields with high selectivity.

Keywords

indium(III) compounds - cyclic allylic acetates - alkylation - aromatics

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References

References and Notes

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General Procedure: A mixture of cyclic allylic acetate (1 mmol), arene or indole (2 mmol) and/or pyrrole or furan (4 mmol) and InCl₃ (10 mol%) in 1,2-dichloroethane (10 mL) was stirred at reflux temperature for the time required to complete the reaction (Table [1] ). After complete conversion as indicated by TLC, the reaction mixture was diluted with water and extracted with EtOAc (2 × 10 mL). The combined organic layers were dried over anhyd Na₂SO₄, concentrated in vacuo and purified by column chromatography on silica gel (Merck, 100-200 mesh, EtOAc-hexane, 1:9) to afford the corresponding cyclohexenyl-substituted aromatic or heteroaromatic compound in pure form.
Spectral Data for Selected Products:
Entry a: ¹H NMR (200 MHz, CDCl₃): δ = 7.80 (br s, 1 H, NH), 7.65 (d, J = 8.0 Hz, 1 H), 6.85-7.40 (m, 4 H), 5.60 (br s, 1 H), 3.65 (br s, 1 H), 2.05 (m, 4 H), 1.75 (s, 3 H), 1.65 (m, 2 H). IR (KBr): 3416, 2920, 2857, 1697, 1453, 1338, 1087, 743 cm^-1. EIMS: m/z (%) = 211 (100) [M⁺], 196 (70), 168 (53), 130 (31), 117 (30), 77 (15), 41 (18). HRMS (LSIMS): m/z [M⁺] calcd for C₁₅H₁₇N: 211.1361; found: 211.1359.
Entry b: ¹H NMR (500 MHz, CDCl₃): δ = 7.70 (br s, 1 H, NH), 7.47 (d, J = 7.1 Hz, 1 H, Ha), 7.25 (d, J = 7.1 Hz, 1 H, Hd), 7.05 (t, J = 7.1 Hz, 1 H, Hc), 7.01 (t, J = 7.1 Hz, 1 H, Hb), 5.74 (q, J = 2.2 Hz, 1 H, H-10), 4.20 (q, J = 7.2 Hz, 2 H, H-11), 3.70 (dddd, J _H4-H10 = 2.2 Hz, J _H4-H5 = 5.6 Hz, J _H4-H5 _′ = 10.0 Hz, J _H4-H7 = 2.0 Hz, 1 H, H-4), 3.24 (dddd, J _H4-H7 = 2.0 Hz, J _H6-H7 = 5.6 Hz, J _H6 _′-H7 = 10.3 Hz, J _H9-H7 = 1.1 Hz, 1 H, H-7), 2.36 (s, 3 H, H-1), 2.13 (m, 1 H, H-6), 1.95-1.98 (m, 2 H, H5, H6′), 1.76-1.78 (m, 4 H, H5′, H-9), 1.29 (t, J = 7.2 Hz, 3 H, H-12). ¹³C NMR (75 MHz, CDCl₃): δ = 135.5 (Ce), 130.1 (C-10), 129.4 (C-2), 126.9 (C=O), 126.9 (Cf), 124.0 (C-8), 120.6 (Cc), 118.8 (Ca), 118.8 (Cb), 115.0 (C-3), 110.2 (Cd), 60.2 (C-11), 46.7 (C-7), 33.2 (C-4), 27.9 (C-5), 26.8 (C-6), 21.5 (C-9), 14.2 (C-12), 11.6 (C-1). IR (KBr): 3390, 2924, 2364, 1721, 1458, 1167, 745 cm^-1. EIMS: m/z (%) = 297 (77) [M⁺], 282 (35), 207 (27), 182 (47), 167 (18), 147 (100), 97 (15), 84 (73), 43 (65).
Entry l: ¹H NMR (200 MHz, CDCl₃): δ = 6.75 (d, J = 8.0 Hz, 1 H), 6.55 (d, J = 8.0 Hz, 1 H), 5.30 (br s, 1 H), 3.85 (s, 9 H), 3.60 (br s, 1 H), 1.95 (m, 3 H), 1.75 (s, 3 H), 1.65 (m, 3 H). ¹³C NMR (50 MHz, CDCl₃, ¹H-decoupled): δ = 151.5, 142.2, 135.0, 132.9, 126.1, 124.7, 122.6, 107.1, 61.1, 60.6, 56.0, 34.7, 31.1, 29.9, 23.9, 21.5. IR (KBr): 3452, 2928, 1601, 1492, 1462, 1280, 1097, 1022, 717 cm^-1. EIMS: m/z (%) = 262 (100) [M⁺], 247 (43), 219 (20), 203 (17), 167 (10), 95 (16), 84 (24), 49 (43). HRMS (LSIMS): m/z [M⁺] calcd for C₁₆H₂₂O₃: 262.1569; found: 262.1565.