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M. Rueping et al.
LETTER
Int. Ed. 2008, 47, 593. (g) Rueping, M.; Antonchick, A. P.
Org. Lett. 2008, 10, 1731. (h) Rueping, M.; Theissmann, T.;
Kuenkel, A.; Koenigs, R. M. Angew. Chem. Int. Ed. 2008,
47, 6798. (i) Rueping, M.; Antonchick, A. P.; Sugiono, E.;
Grenader, K. Angew. Chem. Int. Ed. 2009, 48, 908.
(j) Rueping, M.; Sugiono, E.; Steck, A.; Theissmann, T. Adv.
Synth. Catal. 2010, 352, 281. (k) Rueping, M.; Tato, F.;
Schoepke, F. R. Chem. Eur. J. 2010, 16, 2688.
Tsubogo, T.; Kobayashi, S. J. Am. Chem. Soc. 2007, 129,
5364. (d) Tsubogo, T.; Saito, S.; Seki, K.; Yamashita, Y.;
Kobayashi, S. J. Am. Chem. Soc. 2008, 130, 13321.
(e) Kobayashi, S.; Tsubogo, T.; Saito, S.; Yamashita, Y.
Org. Lett. 2008, 10, 807. (f) Poisson, T.; Yamashita, Y.;
Kobayashi, S. J. Am. Chem. Soc. 2010, 132, 7890.
(g) Poisson, T.; Tsubogo, T.; Yamashita, Y.; Kobayashi, S.
J. Org. Chem. 2010, 75, 963.
(5) (a) Akiyama, T.; Itoh, J.; Yokota, K.; Fuchibe, K. Angew.
Chem. Int. Ed. 2004, 43, 1566. (b) Yamanaka, M.; Itoh, J.;
Fuchibe, K.; Akiyama, T. J. Am. Chem. Soc. 2007, 129,
6756. (c) Itoh, J.; Fuchibe, K.; Akiyama, T. Synthesis 2008,
1319. (d) Akiyama, T.; Katoh, T.; Mori, K.; Kanno, K.
Synlett 2009, 1664.
(12) For our studies on chiral calcium salts in catalysis, see:
(a) Rueping, M.; Theissmann, T.; Kuenkel, A.; Koenigs, R.
M. Angew. Chem. Int. Ed. 2008, 47, 6798. (b) Rueping, M.;
Koenigs, R. M.; Atodiresei, I. Chem. Eur. J. 2010, 16, 9350.
(c) Rueping, M.; Nachtsheim, B. J.; Koenigs, R. M.;
Ieawsuwan, W. Chem. Eur. J. 2010, 16, 13116.
(6) (a) Uraguchi, D.; Terada, M. J. Am. Chem. Soc. 2004, 126,
5356. (b) Gridnev, I. D.; Kouchi, M.; Sorimachi, K.; Terada,
M. Tetrahedron Lett. 2007, 48, 497. (c) Terada, M.;
Machioka, K.; Sorimachi, K. Angew. Chem. Int. Ed. 2006,
45, 2254. (d) Terada, M.; Machioka, K.; Sorimachi, K.
J. Am. Chem. Soc. 2007, 129, 10336. (e) Terada, M.;
Tanaka, H.; Sorimachi, K. Synlett 2008, 1661. (f) Hatano,
M.; Moriyama, K.; Maki, T.; Ishihara, K. Angew. Chem. Int.
Ed. 2010, 49, 3823.
(7) (a) Guo, Q.-X.; Liu, H.; Guo, C.; Luo, S.-W.; Gu, Y.; Gong,
L.-Z. J. Am. Chem. Soc. 2007, 129, 3790. (b) Dagousset,
G.; Drouet, F.; Masson, G.; Zhu, J. Org. Lett. 2009, 11, 5546.
(8) (a) Akiyama, T.; Honma, Y.; Itoh, J.; Fuchibe, K. Adv.
Synth. Catal. 2008, 350, 399. (b) Sickert, M.; Schneider, C.
Angew. Chem. Int. Ed. 2008, 47, 3631. (c) Giera, D. S.;
Sickert, M.; Schneider, C. Synthesis 2009, 3797.
(13) (a) Adair, G.; Mukherjee, S.; List, B. Aldrichimica Acta
2008, 41, 31. (b) Klussmann, M.; Ratjen, L.; Hoffmann, S.;
Wakchaure, V.; Goddard, R.; List, B. Synlett 2010, 2189.
(14) The absolute configuration of the products was obtained
from X-ray crystal structure analysis of compound 6c. On
the basis of this structure the absolute configuration was
assigned to be the S configuration.
(15) General Procedure for Direct Mannich Reaction: In a
typical experiment pyrone 2 or 1,3-cyclohexadione (5; 1.0
equiv), aldimine 3 (1.5 equiv), and the calcium catalyst (5
mol%) were suspended in Bu2O in a screw-capped vial and
the resulting mixture was allowed to stir at –40 °C for 60–72
h. Purification of the crude product by column
chromatography on silica gel afforded the corresponding
product 4 or 6.
(R)-tert-Butyl(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-
yl)(p-tolyl)methylcarbamate (4a): Isolated by column
chromatography (CH2Cl2–acetone, 10:1) as a white solid in
49% yield and 88% ee. The ee was determined by HPLC
using Chiralpak AD-H column [(n-hexane–i-PrOH, 90:10),
flow rate: 0.6 mL/min; major enantiomer: tR = 29.59 min;
minor enantiomer: tR = 22.07 min]; [a]D –6.1 (c = 1.84,
CH2Cl2); mp 173–175 °C. 1H NMR (400 MHz, CDCl3): d =
7.22 (d, J = 8.0 Hz, 2 H), 7.02 (d, J = 8.0 Hz, 2 H), 6.79 (d,
J = 12.0 Hz, 1 H), 6.05 (d, J = 12.0 Hz, 1 H), 5.88 (s, 1 H),
3.41 (s, 1 H), 2.23 (s, 3 H), 2.07 (s, 3 H), 1.39 (s, 9 H).
13C NMR (100 MHz, CDCl3): d = 166.10, 164.94, 161.74,
157.40, 137.67, 136.82, 129.09, 126.12, 102.60, 100.84,
81.11, 28.48, 21.05, 19.85. IR (KBr): 3359, 2980, 1700,
1651, 1530, 1161, 884, 783 cm–1. MS (EI): m/z (%) = 345 (2)
[M+], 339 (30), 251 (41), 230 (58), 200(100), 145 (64), 77
(92).
(d) Sickert, M.; Abels, F.; Lang, M.; Sieler, J.; Birkemeyer,
C.; Schneider, C. Chem. Eur. J. 2010, 16, 2806.
(9) For selected recent examples of organocatalytic asymmetric
direct Mannich reactions, see: (a) Lou, S.; Taoka, B. M.;
Ting, A.; Schaus, S. E. J. Am. Chem. Soc. 2005, 127, 11256.
(b) Enders, D.; Grondal, C.; Vrettou, M.; Raabe, G. Angew.
Chem. Int. Ed. 2005, 44, 4079. (c) Ting, A.; Lou, S.;
Schaus, S. E. Org. Lett. 2006, 8, 2003. (d) Enders, D.;
Grondal, C.; Vrettou, M. Synthesis 2006, 3597. (e) Zhao,
G.-L.; Córdova, A. Tetrahedron Lett. 2006, 47, 7417.
(f) Hasegawa, A.; Naganawa, Y.; Fushimi, M.; Ishihara, K.;
Yamamoto, H. Org. Lett. 2006, 8, 3175. (g) Tillman, A. L.;
Dixon, D. J. Org. Biomol. Chem. 2007, 5, 606. (h) Cheng,
L.; Wu, X.; Lu, Y. Org. Biomol. Chem. 2007, 5, 1018.
(i) Marianacci, O.; Micheletti, G.; Bernardi, L.; Fini, F.;
Fochi, M.; Pettersen, D.; Sgarzani, V.; Ricci, A. Chem. Eur.
J. 2007, 13, 8338. (j) Ramasastry, S. S. V.; Zhang, H.;
Tanaka, F.; Barbas, C. F. III J. Am. Chem. Soc. 2007, 129,
288. (k) Sukach, V. A.; Golovach, N. M.; Pirozhenko, V. V.;
Rusanov, E. B.; Vovk, M. V. Tetrahedron: Asymmetry 2008,
19, 761. (l) Kawanaka, Y.; Phillips, E. M.; Scheidt, K. A.
J. Am. Chem. Soc. 2009, 131, 18028. (m) Pan, Y.; Zhao, Y.;
Ma, T.; Yang, Y.; Liu, H.; Jiang, Z.; Tan, C.-H. Chem. Eur.
J. 2010, 16, 779. (n) Ayaz, M.; Westermann, B. Synlett
2010, 1489.
(R)-tert-Butyl(2-hydroxy-6-oxocyclohex-1-enyl)(p-tolyl)-
methylcarbamate (6a): Isolated by column
chromatography (CH2Cl2–acetone, 10:1) as a white solid in
47% yield and 73% ee. The ee was determined by HPLC
using Chiralpak AD-H column [(n-hexane–i-PrOH, 92:8),
flow rate: 0.6 mL/min; major enantiomer: tR = 20.23 min;
minor enantiomer: tR = 17.98 min]; [a]D +4.43 (c = 0.75,
CH2Cl2); mp 132–134 °C. 1H NMR (400 MHz, CDCl3): d =
10.60 (br s, 1 H), 7.19 (d, J = 8.0 Hz, 2 H), 7.00 (d, J = 8.0
Hz, 2 H), 6.82 (d, J = 9.9 Hz, 1 H), 5.99 (d, J = 9.9 Hz, 1 H),
2.45 (t, J = 6.0 Hz, 2 H), 2.22 (s, 5 H), 1.79–1.89 (m, 2 H),
1.35 (s, 9 H). 13C NMR (100 MHz, CDCl3): d = 173.73,
157.32, 136.00, 128.80, 125.92, 116.22, 80.60, 48.78, 37.02,
29.64, 28.54, 21.15, 20.62. IR (KBr): 3455, 2922, 1710,
1490, 1165, 1025, 779 cm–1. MS (EI): m/z (%) = 331 (56)
[M+], 266 (58), 239 (92), 194 (100), 116 (58), 78 (52), 70
(98).
(10) (a) Rueping, M.; Azap, C. Angew. Chem. Int. Ed. 2006, 45,
7832. (b) Rueping, M.; Sugiono, E.; Schoepke, F. R. Synlett
2007, 1441. (c) Rueping, M.; Lin, M. Y. Chem. Eur. J. 2010,
16, 4169.
(11) For selected examples of chiral Ca(II) salts in catalysis, see:
(a) Suzuki, T.; Yamagiwa, N.; Matsuo, Y.; Sakamoto, S.;
Yamaguchi, K.; Shibasaki, M.; Noyori, R. Tetrahedron Lett.
2001, 42, 4669. (b) Kumaraswamy, G.; Sastry, M. N. V.;
Jena, N. Tetrahedron Lett. 2001, 42, 8515. (c) Saito, S.;
Synlett 2011, No. 3, 323–326 © Thieme Stuttgart · New York