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44, 4564; (c) M. M. Salter, J. Kobayashi, Y. Shimizu and
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H. Mihara, A. Kuramochi, T. Ohshima and M. Shibasaki,
Chem.–Asian J., 2007, 2, 794; (e) G. A. Cutting, N. E. Stainforth,
M. P. John, G. Kociok-Kohn and M. C. Willis, J. Am. Chem. Soc.,
2007, 129, 10632; (f) D. Uraguchi, Y. Ueki and T. Ooi, J. Am. Chem.
Soc., 2008, 130, 14088; (g) S. Kobayashi, R. Yazaki, K. Seki and
Y. Yamashita, Angew. Chem., Int. Ed., 2008, 47, 5613; (h) X.-X. Yan,
Q. Peng, Q. Li, K. Zhang, J. Yao, X.-L. Hou and Y.-D. Wu, J. Am.
Chem. Soc., 2008, 130, 14362; (i) D. Shang, Y. Liu, X. Zhou, X. Liu
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D. Seidel, J. Am. Chem. Soc., 2009, 131, 11648; (k) G. Liang,
M.-C. Tong, H. Tao and C.-J. Wang, Adv. Synth. Catal., 2010,
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Y. Zhu, M. Xie, L. Lin, X. Liu and X. Feng, Chem.–Eur. J., 2011,
17, 2583; (n) G. Lu, T. Yoshino, H. Morimoto, S. Matsunaga and
M. Shibasaki, Angew. Chem., Int. Ed., 2011, 50, 4382; (o) J. Jiang,
H.-D. Xu, J.-B. Xi, B.-Y. Ren, F.-P. Lv, X. Guo and L.-Q. Jiang,
J. Am. Chem. Soc., 2011, 133, 8428; (p) S.-H. Shi, F.-P. Huang, P. Zhu,
Z.-W. Dong and X.-P. Hui, Org. Lett., 2012, 14, 2010;
(q) S. Nakamura, Y. Maeno, M. Ohara, A. Yamamura,
Y. Funahashi and N. Shibata, Org. Lett., 2012, 14, 2960.
Scheme 3 Working stereochemical model.
nucleophile (Scheme 3). In this complex the high steric congestion
imposed by the tert-butyl group at the sulfur atom in close
proximity to the copper center hinders the approach of the
N-sulfonyl imine from the Re C-a enolate face of the azomethine.4
Thus, the approach of I from the more accessible Si C-a enolate
face to the N-sulfonyl imine accounts for the high stereoselectivity
attained in the formation of the C(2S) stereocenter (TS-II).10 The
high syn-diastereocontrol can be tentatively rationalized invoking
a severe steric repulsion of the bulky N-diarylmethylene group in
the ketimine nucleophile with the N-sulfonyl group,4,7b thereby
disfavouring IIIa (leading to anti-configured products) and forcing
the imine to approach from its Si-face via the intermediate IIIb
that would account for the formation of the syn-(2S,3R)-adducts.
In conclusion, an efficient and practical asymmetric
CuI-catalyzed Mannich reaction of glycine derivatives with aliphatic
imines generated in situ from a-amido sulfones has been
devised. b-Alkyl-a,b-diamino acid derivatives are produced
in good yields and excellent diastereo- and enantiocontrol
(typically syn/anti = Z90 : r10 and Z90% ee). The selective
orthogonal N-deprotection under mild conditions is demonstrated.
6 For the highly enantioselective Mannich reaction of a-substituted
azlactones with enolizable aliphatic imines: (a) W.-Q. Zhang,
L.-F. Cheng, J. Yu and L.-Z. Gong, Angew. Chem., Int. Ed., 2012,
51, 4085; (b) A. D. Melhado, G. W. Amarante, Z. J. Wang, M. Luparia
and F. D. Toste, J. Am. Chem. Soc., 2011, 133, 3517. See also ref. 5h.
7 (a) J. Hernandez-Toribio, R. Gomez Arrayas and J. C. Carretero,
J. Am. Chem. Soc., 2008, 130, 16150; (b) J. Hernandez-Toribio,
R. Gomez Arrayas and J. C. Carretero, Chem.–Eur. J., 2010,
16, 1153.
8 Review on applications of a-amido sulfones in asymmetric catalysis:
B. Yin, Y. Zhang and L.-W. Xu, Synthesis, 2010, 3583.
9 (a) N. S. Chowdari, M. Ahmad, K. Albertshofer, F. Tanaka and
C. F. Barbas, III, Org. Lett., 2006, 8, 2839. For the catalytic
asymmetric Mannich reaction of phosphoglycine Schiff bases with
a-amido sulfones, see: (b) R. D. Momo, F. Fini, L. Bernardi and
A. Ricci, Adv. Synth. Catal., 2009, 351, 2283.
10 See ESIz for base, solvent and chiral ligand screening. Catalyst
Acknowledgements
loading of 5 mol% led to decreased reactivity.
11 The absolute and relative configuration of the Mannich products
was determined by preparation of the known compound 260
(methyl ester derivative of product 26) and comparison of the
NMR data and optical rotation with those described in the
literature (see ref. 4 and ESIz).
´
We thank the Ministerio de Ciencia e Innovacion (MICINN,
´
´
CTQ2009-07791) and the Consejerıa de Educacion de la
Comunidad de Madrid (programme AVANCAT, S2009/
PPQ-1634) for financial support. E.H. thanks the Gobierno
Vasco for a predoctoral fellowship.
12 Pioneering work by Kobayashi’s group has revealed that the
nature of the imine pronucleophile can significantly influence its
reactivity and stereoselectivity in Mannich-type reactions:
S. Kobayashi, T. Tsubogo, S. Saito and Y. Yamashita, Org. Lett.,
2008, 10, 807. See also ref. 5g and 7.
Notes and references
1 Reviews on synthesis and biological significance of a,b-diamino acids:
(a) A. Viso, R. Fernandez de la Pradilla, A. Garcıa and A. Flores, Chem.
Rev., 2005, 105, 3167; (b) A. Viso, R. F. de la Pradilla, M. Tortosa,
A. Garca and A. Flores, Chem. Rev., 2011, 111, PR1–PR42.
2 For recent reviews on catalytic asymmetric Mannich reaction:
(a) A. Ting and S. E. Schaus, Eur. J. Org. Chem., 2007, 5797;
(b) J. M. M. Verkade, L. J. C. vanHemert, P. J. L. M. Quaedflieg
and F. P. J. T. Rutjes, Chem. Soc. Rev., 2008, 37, 29.
3 For a recent review on the synthesis of a,b-amino acids via catalytic
asymmetric direct Mannich reaction, see: R. Gomez Arrayas and
J. C. Carretero, Chem. Soc. Rev., 2009, 38, 1940.
4 L. Bernardi, A. S. Gothelf, R. G. Hazell and K. A. Jørgensen,
J. Org. Chem., 2003, 68, 2583.
13 G. Kumaraswamy and A. Pitchaiah, Helv. Chim. Acta, 2011,
94, 1543.
14 For previous catalytic asymmetric Mannich reactions with
formaldehyde-derived imines or iminium ions, see: (a) I. Ibrahem,
J. Casas and A. Cordova, Angew. Chem., Int. Ed., 2004, 43, 6528;
(b) Y. Chi and S. H. Gellman, J. Am. Chem. Soc., 2006, 128, 6804;
(c) I. Ibrahem, W. Zou, J. Casas, H. Sunden and A. Cordova,
Tetrahedron, 2006, 62, 357.
15 For cis- and trans-assignment on imidazolidinones derived from
a,b-diamino acid derivatives, see: S. H. Lee, J. Yoon, S. H. Chung
and Y. S. Lee, Tetrahedron, 2001, 57, 2139.
16 The complex I was found to be the most stable geometry in the
coordination of the metal atom with Fesulphos and the azomethine
species: S. Cabrera, R. Gomez Arrayas, B. Martın-Matute,
F. P. Cossıo and J. C. Carretero, Tetrahedron, 2007, 63, 6587.
5 For examples on glycinate (and related species) Mannich reaction,
see: (a) T. Ooi, M. Kameda, J.-i. Fujii and K. Maruoka, Org. Lett.,
2004, 6, 2397; (b) A. Okada, T. Shibuguchi, T. Ohshima, H. Masu,
c
9624 Chem. Commun., 2012, 48, 9622–9624
This journal is The Royal Society of Chemistry 2012