E. Raluy et al. / Tetrahedron Letters 50 (2009) 4495–4497
4497
Recently, Woodward and co-workers reported for the first time
the advantages of using DABAL–Me as an air-stable methylating
Prieto, O.; Woodward, S. Pure Appl. Chem. 2006, 78, 511; (c) Mata, Y.; Diéguez,
M.; Pàmies, O.; Woodward, S. J. Org. Chem. 2006, 71, 8159; (d) Mata, Y.; Diéguez,
M.; Pàmies, O.; Woodward, S. Inorg. Chim. Acta 2008, 361, 1381.
Ligands L1-L4a–c have been successfully applied in the Pd-catalyzed allylic
substitution reaction and in the Rh-catalyzed hydrogenation. See: (a) Diéguez,
M.; Ruiz, A.; Claver, C. Chem. Commun. 2001, 2702; (b) Diéguez, M.; Ruiz, A.;
Claver, C. Tetrahedron: Asymmetry 2001, 12, 2827; (c) Raluy, E.; Claver, C.;
3
4a
reagent in nickel-catalyzed additions to aldehydes. Our results
using this reagent indicate that the catalytic performance follows
the same trend as for the trimethylaluminium addition to alde-
hydes, which is not unexpected because the reactions have a sim-
ilar mechanism. However, the yields were lower than in
trimethylaluminium addition (Table 2, entries 11–13).
In summary, we have described the first successful application
of bidentate ligands in the asymmetric Ni-catalyzed trialkylalu-
minium addition to several aldehydes. These phosphite–phosp-
horoamidite ligands have the advantage that they are easily
5
.
.
6
The new ligands L3d and L3e were prepared following the same procedure as for
3
1
the preparation of L1–L4a–c. Ligand L3d: yield: 0.42 g, 57%. P NMR (C
6 6
D ), d:
36.7 (s), 144.2 (s). 1H NMR (C
1
6
D
6
), d: 1.04 (s, 3H, CH ), 1.26 (s, 3H, CH ), 2.05 (s,
3H, CH ), 2.07 (s, 6H, CH ), 2.08 (s, 3H, CH ), 2.18 (s, 3H, CH ), 2.28 (s, 3H, CH ),
), 3.03 (m, 1H, NH), 3.79 (m, 1H, H-3), 4.16 (m,
3
3
3
3
3
3
3
2
1
1
.29 (s, 6H, CH
3
), 2.32 (s, 3H, CH
3
0
3
H, H-5), 4.23 (m, 2H, H-4, H-5 ), 4.32 (d, 1H, H-2,
J
1–2 = 4.0 Hz), 5.59 (d, 1H, H-
), d: 17.1 (CH ), 17.2
= 6.8 Hz),
3
13
,
J
1–2 = 4.0 Hz), 6.7–7.2 (m, 8H, CH@). C NMR (C
6
D
6
3
prepared in a few steps from commercial
D
-xylose and
D
-glucose,
(CH ), 17.3 (CH ), 21.2 (CH ), 26.8 (CH ), 27.2 (CH ), 58.2 (d, C-3, J
C–P
3
3
3
3
3
6
(
1
3.8 (C-5), 79.3 (C-4), 87.0 (C-2), 105.0 (C-1), 112.1 (CMe
CH@), 129.7 (CH@),130.3 (C), 130.4 (C), 130.5 (C), 131.6 (CH@), 131.8 (CH@),
32.3 (CH@), 133.8 (C), 134.1 (C), 134.3 (C), 147.1 (C), 147.2 (C), 147.3 (C), 147.5
(C). Anal. Calcd for C40H45NO P : C, 65.84; H, 6.22; N, 1.92. Found: C, 65.76; H,
2
), 126.0 (CH@), 128.9
inexpensive natural chiral feedstocks. In addition, their furanoside
backbone and biaryl moieties can be easily tuned so that their ef-
fect on catalytic performance can be explored. By carefully select-
ing the ligand components, we obtained high activities and
enantioselectivities. These results open up a new class of ligands
8
2
31
6 6
6.19; N, 1.90. Ligand L3e: yield: 0.39 g, 50%. P NMR (C D ), d: 142.3 (s), 145.2
1
(
s). H NMR (C
6
D
6
), d: 1.04 (s, 3H, CH
3
), 1.25 (s, 3H, CH
3
), 3.11 (m, 1H, NH), 3.43
0
(
m, 1H, H-3), 3.58 (m, 5H, H-4, CH
2
), 4.08 (m, 1H, H-5), 4.19 (m, 2H, H-4, H-5 ),
(
bidentated phosphite–phosphoroamidite) for the nickel-catalyzed
3
4
J
2
J
(
1
(
1
.42 (d, 1H, H-2,
J
1–2 = 3.6 Hz), 5.09 (m, 4H, CH
1–2 = 3.6 Hz), 5.94 (m, 2H, CH@), 6.8–7.2 (m, 12H, CH@). C NMR (C
6.8 (CH ), 27.3 (CH ), 35.0 (CH ), 35.1 (CH ), 35.3 (CH ), 35.6 (CH ), 53.6 (d, C-3,
C–P = 7.2 Hz), 63.9 (d, C-5, JC–P = 3.6 Hz), 80.6 (C-4), 85.6 (C-2), 104.9 (C-1), 112.5
CMe ), 116.7 (CH =), 116.8 (CH =), 125.6 (CH@), 125.9 (CH@), 129.0 (CH@)
29.4 (CH@), 129.6 (CH@), 130.3 (CH@), 132.6 (C), 132.8 (C), 133.2 (C), 136.9
CH = allyl), 137.7 (CH = allyl), 137.9 (CH = allyl), 138.1 (CH = allyl), 148.7 (C),
49.1 (C), 149.3 (C). Anal. Calcd for C44 45NO : C, 67.95; H, 5.83; N, 1.80.
Found: C, 67.99; H, 5.86; N, 1.81.
2
=), 5.48 (d, 1H, H-1,
3
13
trialkylaluminium addition to aldehydes. Mechanistic studies and
further modifications in both the sugar backbone and the func-
tional groups are currently being made.
6 6
D ), d:
3
3
2
2
2
2
2
2
2
Acknowledgements
H
8 2
P
We thank the Spanish Government (Consolider Ingenio
CSD2006-0003, CTQ2007-62288/BQU, 2008PGIR/07 to O.P. and
7. See for instance: (a) Feringa, B. L. Acc. Chem. Res. 2000, 33, 346; (b) Diéguez, M.;
Pàmies, O.; Claver, C. Chem. Rev. 2004, 104, 3189; (c) Diéguez, M.; Pàmies, O.;
Ruiz, A.; Díaz, Y.; Castillón, S.; Claver, C. Coord. Chem. Rev. 2004, 248, 2165; (d)
Diéguez, M.; Ruiz, A.; Claver, C. Dalton Trans. 2003, 2957; (e) Pàmies, O.; Diéguez,
M.; Ruiz, A.; Claver, C. Chemistry Today 2004, 12; (f) Diéguez, M.; Pàmies, O.;
Ruiz, A.; Claver, C. In Methodologies in Asymmetric Catalysis; Malhotra, S. V., Ed.;
American Chemical Society: Washington DC, 2004; (g) Diéguez, M.; Pàmies, O.;
Claver, C. Tetrahedron: Asymmetry 2004, 15, 2113; (h) Diéguez, M.; Claver, C.;
Pàmies, O. Eur. J. Org. Chem. 2007, 4621; (i) Minnaard, A. J.; Feringa, B. L.; Lefort,
L.; de Vries, J. G. Acc. Chem. Res. 2007, 40, 1267; (j) Börner, A. Phosphorous Ligands
in Asymmetric Catalysis; Wiley-VCH: Weinheim, 2008.
2
008PGIR/08 to M.D.) and the Catalan Government
(
2005SGR007777) for financial support.
References and notes
1
2
.
.
Pu, L.; Yu, H. B. Chem. Rev. 2001, 101, 757.
Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 5th ed.; Wiley: New
York, 1988.
8. In a typical experiment: [Ni(acac)
(2.33 mol, 1 mol %) were stirred in dry THF (2 mL) under argon atmosphere at
ꢁ20 °C for 10 min. Neat aldehyde (0.25 mmol) was then added and
trialkylaluminium (0.5 mmol) was added dropwise after further 10 min.
After the desired reaction time, the reaction was quenched with 2 M HCl (2 mL).
Then dodecane (20 L) was added and the mixture was extracted with Et
(10 mL). The organic layer was dried over MgSO and analyzed by GC.
2
] (0.6 mg, 2.33 lmol, 1 mol %) and ligand
3
.
(a) Chan, A. S. C.; Zhang, F.-Y.; Yip, C.-W. J. Am. Chem. Soc. 1997, 119, 4080; (b)
Pagenkopf, B. L.; Carreira, E. M. Tetrahedron Lett. 1998, 39, 9593; (c) Lu, J.-F.; You,
J.-S.; Gau, H.-M. Tetrahedron: Asymmetry 2000, 11, 2531; (d) You, J.-S.; Hsieh, S.-
H.; Gau, H.-M. Chem. Commun. 2001, 1546.
l
a
4
.
(a) Biswas, K.; Prieto, O.; Goldsmith, P. J.; Woodward, S. Angew. Chem., Int. Ed.
l
2
O
2
005, 44, 2232; (b) Biswas, K.; Chapron, A.; Cooper, T.; Fraser, P. K.; Novak, A.;
4