Cation Radical Imino Diels-AlderReaction: A New Approach for the Synthesis of Tetrahydroquinolines

Abstract

Cycloaddition of N-arylimines with α-methylstyrenesor 2,3-dihydrofuran was efficiently catalyzed by tris(4-bromophenyl)aminiumhexachloroantimonate (Ar₃N ⁺ ˙SbCl₆ ^- ) producing tetrahydroquinolinederivatives in excellent yields. The reaction was controlled sensitivelyby the oxidation potentials of the imine and the dienophile.

cation radical - imines - tetrahydroquinolines - cycloaddition

References

<A NAME="RU10803ST-1A">1a</A> Weinreb SM. In ComprehensiveOrganic Synthesis   Vol. 5:  Trost BM. Fleming I. Pergamon; Oxford: 1991.  p.401 

<A NAME="RU10803ST-1B">1b</A> Boger DL. Weinreb SM. HeteroDiels-Alder Methodology in Organic Synthesis   Academic; San Diego: 1987.  Chap.2.

<A NAME="RU10803ST-1C">1c</A> Boger DL. Weinreb SM. HeteroDiels-Alder Methodology in Organic Synthesis   Academic; SanDiego: 1987.  Chap. 9.

<A NAME="RU10803ST-1D">1d</A> Qiang LG. Baine NH. J.Org. Chem.  1988,  53:  4218 

<A NAME="RU10803ST-2A">2a</A> Povarov LS. Russ. Chem. Rev.  1967,  36:  656 

<A NAME="RU10803ST-2B">2b</A> Kametani T. Takeda H. Suzuki Y. Honda T. Synth. Commun.  1985,  15:  499 

<A NAME="RU10803ST-2C">2c</A> Kobayashi S. Ishitani H. Nagayama S. Synthesis  1995,  1195 

<A NAME="RU10803ST-2D">2d</A> Yamanaka M. Nishida A. Nakagana M. Org.Lett.  2000,  2:  159 

<A NAME="RU10803ST-2E">2e</A> Hattori K. Yamamoto H. Tetrahedron  1993,  49:  1749 

<A NAME="RU10803ST-2F">2f</A> Grieco PA. Bahsas A. TetrahedronLett.  1988,  29:  5855 

<A NAME="RU10803ST-2G">2g</A> Bortototti B. Leardini R. Nanni D. Zanardi G. Tetrahedron  1993,  49:  10157 

<A NAME="RU10803ST-3A">3a</A> Nagarajan R. Chitra S. Perumal PT. Tetrahedron  2001,  57:  3419 

<A NAME="RU10803ST-3B">3b</A> Sunderanrajan G. Prabagaran N. Varghese B. Org.Lett.  2001,  3:  1973 

<A NAME="RU10803ST-3C">3c</A> Collin J. Jaber N. Lannou MI. TetrahedronLett.  2001,  42:  7405 

<A NAME="RU10803ST-3D">3d</A> Xia C. Heng L. Ma D. TetrahedronLett.  2002,  43:  9405 

<A NAME="RU10803ST-4">4</A> Ma Y. Qian C. Xie M. Sun J. J.Org. Chem.  1999,  64:  6462 

<A NAME="RU10803ST-5A">5a</A> Bauld NL. Tetrahedron  1989,  45:  5307 

<A NAME="RU10803ST-5B">5b</A> Bauld NL. Bellville DJ. Harirchian B. Lorenz KT. Pabon PA. Reynolds DW. Wirth DD. Chiou H.-S. Marsh BK. Acc.Chem. Res.  1987,  20:  371 

<A NAME="RU10803ST-5C">5c</A> Schmittel M. Burghart A. Angew. Chem., Int. Ed. Engl.  1997,  36:  2550 

<A NAME="RU10803ST-6A">6a</A> Behforouz M. Ahmadian M. Tetrahedron  2000,  56:  5259 

<A NAME="RU10803ST-6B">6b</A> Peglow T. Blechert S. Steckhan E. Chem. Commun.  1999,  433 

<A NAME="RU10803ST-6C">6c</A> Wiest O. Steckhan E. Angew. Chem., Int. Ed. Engl.  1993,  32:  901 

<A NAME="RU10803ST-6D">6d</A> Gürtler CF. Blechert S. Steckhan E. Angew. Chem., Int. Ed. Engl.  1995,  34:  1900 

<A NAME="RU10803ST-7A">7a</A> Zhang W. Jia X. Yang L. Liu Z.-L. TetrahedronLett.  2002,  43:  9433 

<A NAME="RU10803ST-7B">7b</A> Zhang J. Jin M.-Z. Zhang W. Yang L. Liu Z.-L. TetrahedronLett.  2002,  43:  9687 

<A NAME="RU10803ST-7C">7c</A> Mao YZ. Jin MZ. Liu Z.-L. Wu LM. Org. Lett.  2000,  2:  741 

<A NAME="RU10803ST-7D">7d</A> Jin M.-Z. Zhang D. Yang L. Liu Y.-C. Liu Z.-L. TetrahedronLett.  2000,  41:  7357 

<A NAME="RU10803ST-7E">7e</A> Jin M.-Z. Yang L. Wu L.-M. Liu Y.-C. Liu Z.-L. Chem.Commun.  1998,  2451 

<A NAME="RU10803ST-8">8</A>

RepresentativeSpectral Data of the Products. syn-3b: Yellow needles, mp 174-176 °C(uncor.). HR-ESI-MS: 379.1211 (calcd for C₂₂H₁₉N₂O₂Cl + H⁺:379.1208). ¹H NMR (400 MHz, CDCl₃): δ = 1.63(s, 3 H, CH₃), 1.98 (dd, J = 2.7,13.4 Hz, 1 H, H-3e), 2.24 (dd, J = 11.4,13.4 Hz, 1 H, H-3a), 4.74 (dd, J = 2.7,11.4Hz, 1 H, H-2), 6.61 (d, J = 8.5Hz, 1 H, H-8), 6.67 (d, J = 2.3Hz, 1 H, H-5), 7.0 (dd, J = 2.3,8.5 Hz, 1 H, H-7), 7.22-7.31 (m, 5 H, Ph), 7.62 (d, 2 H, J = 8.7 Hz,Ar), 8.19 (d, 2 H, J = 9.19,Ar). ¹³C NMR (100.08 MHz, CDCl₃): δ = 29.6(CH₃), 42.3 (C-4), 48.9 (CH₂), 53.8 (CH),116.5 (C-8), 123.8 (C-6), 126.4 (C-5), 127.1 (2 C, Ph), 127.6 (1C, Ph), 128.0 (2 C, Ph), 128.3 (C-7), 129.3 (2 C, Ph), 129.7 (2C, Ph), 132.0 (1 C, Ph), 142.0 (1 C, Ph), 147.5 (1 C, Ph), 148.4(C-10), 150.6 (C-9). anti -3b:Yellow needles, mp 152-153 °C (uncor.).HR-ESI-MS: 379.1210 (calcd. for C₂₂H₁₉N₂O₂Cl + H⁺:379.1208). ¹H NMR (400 MHz, CDCl₃): δ = 1.76(s, 3 H, CH₃), 2.08 (dd, J = 12.0,13.1 Hz, 1 H, H-3a), 2.25 (dd, J = 3.0, 13.1, 1 H, H-3e),4.13 (dd, J = 3.0,12.0 Hz, 1 H, H-2), 6.62 (d, J = 8.5 Hz,H-8), 6.81 (dd, J = 7.0,7.0 Hz, H-6), 7.18 (d, J = 2.2Hz, 1 H, H-5), 7.19-7.35 (m, 5 H, Ph), 7.46 (d, J = 7.2 Hz,2 H, Ar), 8.16 (d, J = 7.2Hz, 2 H, Ar). ¹³C NMR (100.08 MHz, CDCl₃): δ = 29.3(CH₃), 41.7 (C-4), 47.5 (CH₂), 53.9 (CH), 116.1(C-8), 122.4 (C-6), 123.7 (C-5), 126.3 (2 C, Ph), 126.6 (2 C, Ph),127.5 (2 C, Ph), 127.8 (2 C, Ph), 128.1 (C-7), 128.5 (2 C, Ph),142.1 (1 C, Ph), 147.5 (1 C, Ph), 144.6 (C-10), 150.4 (C-9). Thecoupling constants of H-2 suggest its axial conformation in both syn- and anti-3b. The significant low-field shift ofH-3e and up-field shift of H-2 of anti-3b in comparison with those of syn-3b suggestsan axial 4-phenyl group in anti-3b while an equatorial 4-phenyl group in syn-3b. Thestereochemistry was confirmed by their NOESY spectra which showa clear cross peak between the 4-methyl and H-2 in syn-3b, while no such correlation in anti-3b.

<A NAME="RU10803ST-9">9</A> Weinberg NL. Weinberg HR. Chem. Rev.  1968,  68:  449 

<A NAME="RU10803ST-10">10</A>

The oxidation peak potential was determinedvs. SCE by cyclic voltammetry in MeCN using a glassy carbon electrode.

<A NAME="RU10803ST-11">11</A>

The structures of the products wereidentified by comparing their ¹H and ¹³CNMR data with those reported in the literature. See ref. [4]