7420
G.-L. Zhao, A. Co´rdova / Tetrahedron Letters 47 (2006) 7417–7421
11. Ibrahem, I.; Zou, W.; Engqvist, M.; Xu, Y. Chem. Eur. J.
Ar
Ar
Ar
2005, 11, 7024.
Ar
OTMS
H
TMSO
Ar
12. (a) Yoshida, T.; Morimoto, H.; Kumagai, N.; Matsunaga,
S.; Shibasaki, M. Angew. Chem., Int. Ed. 2005, 44, 3470;
(b) Kano, T.; Yamaguchi, Y.; Tokuda, O.; Maruoka, K. J.
Am. Chem. Soc. 2005, 127, 16408; (c) Mitsumori, S.;
Zhang, H.; Cheong, P. H.-Y.; Houk, K. N.; Tanaka, F.;
Barbas, C. F., III. J. Am. Chem. Soc. 2006, 128, 1040; (d)
Trost, B. M.; Jaratjaroonphong, J.; Reutrakul, U. J. Am.
Chem. Soc. 2006, 128, 2778.
R
N
N
N
EtO2C
H
EtO2C
R
II
I
NH
H
EtO2C
13. For an iridium-catalyzed reductive Mannich-type reaction
see: Townes, J. A.; Evans, M. A.; Queffelec, J.; Taylor, S.
J.; Morken, J. P. Org. Lett. 2002, 4, 2537.
14. For selected examples of organocatalytic asymmetric
domino and cascade reactions see: (a) Huang, Y.; Walji,
A. M.; Larsen, C. H.; MacMillan, D. W. C. J. Am. Chem.
Soc. 2005, 127, 15051; (b) Yang, J. W.; Hechavarria
Fonseca, M. T.; List, B. J. Am. Chem. Soc. 2005, 127,
Figure 2. Proposed reaction pathway I and transition state II for
the protected diarylprolinol catalyzed direct asymmetric reductive
Mannich-type reaction.
Acknowledgements
We gratefully acknowledge the Swedish National Re-
search Council, Carl-Trygger Foundation, Lars-Hierta
Foundation, and Medivir AB for financial support.
´
15036; (c) Marigo, M.; Schulte, T.; Franzen, J.; Jørgensen,
K. A. J. Am. Chem. Soc. 2005, 127, 15710; (d) List, B.
Chem. Commun. 2006, 819; (e) Yamamoto, Y.; Momi-
yama, N.; Yamamoto, H. J. Am. Chem. Soc. 2004, 126,
5962; (f) Ramachary, D. B.; Chowdari, N. S.; Barbas, C.
References and notes
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(16 mg, 10 mol %) in CHCl3 (2 mL) was cooled to ꢀ20 °C.
To this solution was added benzoic acid (6 mg, 0.05 mmol,
10 mol %) and Hantzsch ester (140 mg, 0.55 mmol). The
reaction mixture was stirred at ꢀ20 °C for 63 h, after
which the solvent was removed and the residue was
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19. A solution of aldehyde 2 (0.5 mmol) and catalyst 1a
(16 mg, 10 mol %) in CHCl3 (2 mL) was cooled to ꢀ20 °C.
To this solution was added benzoic acid (6 mg, 0.05 mmol,
10 mol %) and Hantzsch ester (140 mg, 0.55 mmol). The
resulting yellow suspension was stirred at ꢀ20 °C for
63 h. Next, the reaction temperature was increased to
+4 °C and N-PMP-protected a-iminoglyoxylate (34 mg,
0.17 mmol) was added. The reaction mixture was stirred
for 24 h at +4 °C. Next, the solvent was removed and the
residue was purified by silica-gel column chromatography
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