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Y.-Q. Cheng et al. / Tetrahedron: Asymmetry 20 (2009) 1753–1758
4.4. Organocatalyst 2a
136.9, 149.0, 158.1, 169.1. 1H NMR of minor rotamer (600 MHz,
CDCl3): d 1.42–1.78 (m, 5H), 2.45–2.52 (m, 2H), 1.90 (m, 1H), 2.69
(m, 1H), 2.83 (m, 1H), 2.97 (m, 1H), 3.30 (m, 1H), 4.39 (m, 1H), 4.61
(m, 1H), 5.29 (d, 1H), 7.13–7.20 (m, 2H), 7.68 (m, 1H), 8.60 (d, 1H);
13C NMR of minor rotamer (150 MHz, DMSO-d): d 19.4, 24.7, 28.6,
38.3, 40.0, 53.5, 56.3, 56.7, 69.7, 121.3, 122.1, 137.1, 149.2, 158.2,
168.9.
Compound 2a was obtained in a 90% yield from (S)-2-(20-piperid-
inyl)pyridine and N-tert-butoxycarbonyl-L-proline (two steps) as a
white solid. ½a 2D0
ꢁ
¼ ꢂ198:4 (c 0.64, CH2Cl2). 1H NMR of major rot-
amer (600 MHz, CDCl3): d 1.26 (t, J = 6.6 Hz, 1H), 1.57 (m, 1H),
1.65–1.67 (m, 2H), 1.75 (m, 1H), 1.83 (m, 3H) 2.18–2.20 (m, 1H),
2.62 (d, J = 13.2 Hz, 1H), 2.93 (q, J = 7.8 Hz, 1H), 3.18 (t, J = 12.0 Hz,
1H), 3.23 (m, 1H), 3.77 (m, 1H), 4.13 (m, 1H), 5.92 (s, 1H), 7.11–
7.13 (m, 2H), 7.64 (t, J = 7.2 Hz, 1H), 8.56 (d, J = 2.4 Hz, 1H); 13C
NMR of major rotamer (150 MHz, CDCl3): d 19.8, 25.8, 26.3, 27.3,
30.6, 42.4, 47.7, 53.3, 58.4, 121.3, 121.5, 136.5, 149.1, 159.4, 173.1.
1H NMR of minor rotamer (600 MHz, CDCl3): d 1.35 (q, J = 12.6 Hz,
1H), 1.55–1.57 (m, 2H), 1.65–1.67 (m, 1H), 1.75 (m, 2H), 1.83 (m,
2H), 2.18–2.21 (m, 1H), 2.67 (t, J = 12.6 Hz, 1H), 2.81 (m, 1H), 2.86
(d, J = 13.2 Hz, 1H), 3.23 (m, 1H), 3.77 (m, 1H), 4.60–4.63 (m, 1H),
5.14 (s, 1H), 7.20–7.21 (m, 2H), 7.67 (t, J = 7.2 Hz, 1H), 8.61 (d J =
2.4 Hz, 1H); 13C NMR of minor rotamer (150 MHz, CDCl3):
d 19.8, 25.1, 26.6, 27.9, 31.5, 39.1, 47.7, 56.6, 58.3, 121.0, 122.0,
137.0, 149.6, 158.3, 174.3.
References
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4.5. Organocatalyst 2b
Compound 2b was obtained in a 93% yield from (R)-2-(20-pipe-
ridinyl)pyridine and N-tert-butoxycarbonyl-L-proline (two steps)
as a white solid. ½a D20
ꢁ
¼ þ70:0 (c 1, CH2Cl2). 1H NMR of major rot-
amer (600 MHz, CDCl3): d 1.51–1.56, 1.58–1.60, 1.68–1.70, 1.79,
1.87 (m, 8H), 2.19 (m, 1H), 2.71–2.77 (m, 1H), 2.91 (m, 1H),
3.12–3.16 (m, 1H), 3.21–3.23 (m, 1H), 3.79 (d, J = 13.2 Hz, 1H),
4.07 (t, J = 6.0 Hz, 1H), 5.94 (s, 1H), 7.13–7.17 (m, 2H), 7.62 (t,
J = 7.2 Hz, 1H), 8.57 (s, 1H); 13C NMR of major rotamer (150 MHz,
CDCl3): d 19.8, 25.9, 26.4, 26.9, 31.2, 42.2, 47.5, 53.6, 58.5, 121.6,
121.7, 136.6, 149.1, 158.9, 173.1. 1H NMR of minor rotamer
(600 MHz, CDCl3): d 1.32 (m, 1H), 1.51–1.56, 1.58–1.60, 1.68–
1.70, 1.79, 1.87 (m, 9H), 2.78 (m, 1H), 2.85 (m, 1H), 3.12–3.16
(m, 1H), 4.01 (m, 1H), 4.64 (d, J = 12.0 Hz, 1H), 5.26 (s, 1H), 7.13–
7.17 (m, 2H), 7.68 (m, 1H), 8.62 (s, 1H); 13C NMR of minor rotamer
(150 MHz, CDCl3): d 19.8, 25.3, 26.4, 28.8, 30.7, 39.5, 47.3, 57.2,
58.7, 121.1, 121.9, 136.6, 149.6, 158.9, 173.1.
4.6. Organocatalyst 2d
Compound2d was obtained in a 87% yieldfrom (R)-2-(20-piperid-
inyl)pyridine and N-tert-butoxycarbonyl-trans-4-hydroxy-L-proline
(two steps) as a white solid. ½a D20
ꢁ
¼ þ61:7 (c 0.47, CH2Cl2). 1H NMR of
major rotamer (600 MHz, CDCl3): d 1.42–1.78 (m, 5H), 2.00 (m, 1H),
2.31 (m, 1H), 2.69 (m, 1H), 3.05 (d, J = 16.8 Hz, 1H), 3.16 (m, 1H), 3.30
(m, 1H), 3.79 (d, J = 19.8 Hz, 1H), 4.44 (t, J = 11.4 Hz, 1H), 4.53 (s, 1H),
5.90 (d, J = 5.4 Hz, 1H), 7.13–7.20 (m, 2H), 7.67 (m, 1H), 8.57 (d,
J = 6 Hz, 1H); 13C NMR of major rotamer (150 MHz, DMSO-d):
d 19.4, 25.1, 26.9, 38.4, 42.2, 53.3, 53.7, 56.8, 69.8, 121.3, 121.9,