674
X.D. Jia et al. / Chinese Chemical Letters 22 (2011) 671–674
moderate yield and trans-isomers were preferred [24]. In such process, enol ethers could serve as surrogates of
acetaldehyde to participate in the tandem cyclizatioin, avoiding the isolation of the unstable acetaldehyde imines
(Scheme 1).
In summary, we have executed an efficient approach in which the tandem cyclization between substituted anilines and
enol ethers occurred to achieve the synthesis of a series of tetrahydroquinoline derivatives. We are currently focused on
promoting this interesting transformation and further exploring the use in construction of more variable heterocycle
compounds. Further research insight into the mechanism of this reaction is also underway in this laboratory.
Acknowledgments
We thank NSFC (No. 21002079) and Project (No. 20096203120002) supported by the Ministry of Education of the
People’s Republic of China. We also thank the third Knowledge and Technological Innovation Project (No. NWNU-
KJCXGC-03-75 and NWNU-KJCXGC-03-64) of Northwest Normal University for supporting our research.
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1
22] Representative spectral data of the products. 3a: Cis-isomer: H NMR (400 MHz, CDCl
3
): d 1.57–1.90 (m, 5H), 2.04 (m, 1H), 2.60–2.67 (m,
1
H), 3.43–3.46 (m, 1H), 3.69–3.71 (m, 2H), 3.80–3.82 (m, 2H), 5.12 (d, 1H, J = 8.0 Hz), 6.52 (d, J = 8.0 Hz, 1H), 6.74–6.78 (m, 1H), 7.03–7.07
1
(
m, 1H), 7.30 (d, 1H, J = 7.6 Hz); trans-isomer: H NMR (400 MHz, CDCl
3
): d 1.57–1.90 (m, 5H), 2.13–2.26 (m, 1H), 2.80–2.85 (m, 1H),
.69–3.71 (m, 2H), 3.80–3.82 (m, 2H), 3.94–3.99 (m, 1H), 3.57 (d, 1H, J = 5.6 Hz), 6.63 (d, 1H, J = 8.0 Hz), 6.74–6.78 (m, 1H), 7.08–7.12 (m,
H), 7.34 (d, 1H, J = 7.6 Hz); EI–MS m/z (relative intensity, %): 233 (22.1%), 174 (100%), 144 (16.3%), 130 (35.4%).
3
1
1
[
23] Representative spectral data of the products. syn-4e: H NMR (400 MHz, CDCl
3
): d 1.57–1.62 (m, 4H), 1.71–1.97 (m, 6H), 2.52–2.58 (m, 1H),
3
7
1
2
.34–3.39 (m, 2H), 3.61–3.68 (m, 1H), 3.72–3.75 (m, 2H), 3.78–3.84 (m, 2H), 4.97 (d, 1H, J = 8.0 Hz), 5.05 (d, 1H, J = 4.0 Hz), 6.40 (brs, 1H),
13
3
.05 (d, 1H, J = 8.4 Hz), 7.35 (s, 1H); C NMR (100.6 MHz, CDCl ): d 23.5, 23.7, 26.3, 31.2, 32.3, 32.4, 42.2, 42.3, 52.0, 66.6, 66.9, 75.2,
10.0, 115.9, 124.6, 130.9, 132.5, 143.8; EI–MS m/z (relative intensity, %): 383 (1.5%), 381 (1.1%), 254 (16.7%), 252 (18.6%), 210 (3.7%),
08 (2.7%), 143 (3.9%), 71 (100%). Crystallographic data for the structure analysis have been deposited at the Cambridge Crystallographic
Data Centre as supplementary publication, CCDC No. 790498 for syn-4e.
1
24] Representative spectral data of the products. trans-5d: H NMR (400 MHz, CDCl
[
3
): d 1.21 (d, 3H, J = 5.6 Hz), 1.50 (t, 1H, J = 10.8 Hz), 2.09 (d,
1
H, J = 13.2 Hz), 3.38 (brs, 1H), 3.89 (br, NH, 2H), 4.43 (brs, 1H), 6.43 (d, 1H, J = 8.8 Hz), 6.52 (d, 2H, J = 8.4 Hz), 7.13 (d, 1H, J = 7.6 Hz), 7.27
1
br, 3H); C NMR (100.6 MHz, CDCl
3
(
(
(
(
3
): d 21.8, 34.4, 42.3, 48.6, 108.4, 108.8, 114.2, 116.1, 122.4, 131.4, 132.0, 133.0, 143.9, 144.9; EI–MS m/z
relative intensity, %): 398 (0.7%), 396 (1.5%), 394 (0.8%), 226 (29.0%), 224 (45.5%), 210 (86.9%), 208 (94.4%), 173 (89.5%), 171 (85.1%), 145
1
19.4%), 143 (24.8%), 129 (57.9%), 65 (100%); ESI-HRMS: m/z Calcd. for C16
300 MHz, CDCl ):d1.22(d, 3H, J = 6.3 Hz), 1.45(q, 1H, J = 11.7 Hz), 2.31 (ddd, 1H, J = 2.1, 5.1, 12.9 Hz), 3.58 (ddd, 1H, J = 2.4, 5.7, 11.1 Hz),
.78 (br, NH, 2H), 4.70 (dd, 1H, J = 5.4, 11.1 Hz), 6.38 (d, 1H, J = 9.0 Hz), 6.55 (d, 2H, J = 9.0 Hz), 7.11 (dd, 1H, J = 2.4, 8.4 Hz), 7.25–7.30 (m,
14 2 2
H N Br + H: 392.9597, found: 392.9603; cis-5d: H NMR
3
3
2
1
3
13
3
H), 7.43 (s, 1H); C NMR (100.6 MHz, CDCl ): d 22.2, 37.1, 46.9, 50.2, 109.0, 114.7, 115.5, 124.6, 129.6, 130.9, 132.1, 143.8, 146.4, one C
siganllostforoverlap;EI-MSm/z(relativeintensity, %):398(1.6%), 396(3.1%), 394(1.6%), 226(66.0%),224(77.1%),210(100%), 208(91.6%),
73 (82.7%), 171 (85.2%); ESI-HRMS: m/z Calcd. for C16 Br +H: 392.9597, found: 392.9601.
1
H N
14 2
2