A New Pyridyl Bis(oxazoline) Ligand Prepared from d-Glucosamine
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References
Experimental Section
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Procedure for the Preparation of glucoPybox (4)
from Bis(amide)2
N
Bis(amide) 2 (3.60 g, 7.36 mmol), obtained as described previ-
A
ously,[5,6] was taken up in acetyl chloride (40 mL) and stirred
at room temperature. The progress of the reaction was moni-
tored by TLC (petroleum ether/ethyl acetate, 1:3). After 16 h
the acetyl chloride was removed under vacuum and the resi-
due was twice co-evaporated with toluene. The raw chloride
3 was then dissolved in dry acetonitrile (40 mL), Et4NCl
(2.63 g, 15.8 mmol) and solid NaHCO3 (2.63 g, 31.30 mmol)
were added. The resulting mixture was stirred for 16 h at
room temperature. The reaction was monitored by TLC (pe-
troleum ether/ethyl acetate, 1:3). The solvent was removed
under vacuum, the residue was taken up in dichloromethane
(50 mL) and washed with water (50 mL). The organic phase
was dried over MgSO4, filtered and concentrated. The raw
product was purified by flash chromatography on silica gel
(first eluting with petroleum ether/ethyl acetate, 1:2, and fi-
nally with pure ethyl acetate) affording pybox ligand 4 as a
yellow foam; yield: 2.16 g (3.07 mmol, 42%); 1HNMR
(CDCl3, 400 MHz, ppm): d=8.18 (2H, d, J=7.9 Hz, pyridine
H), 7.88 (1H, t, J=7.9 Hz, pyridine H), 6.21 (2H, d, J=7.5,
H-1), 5.31 (2H, dd ꢁ t, J=2.7 Hz, H-3), 4.88 (2H, ddd, J=
1.0, 2.7, 7.5 Hz, H-4), 4.35 (2H, ddd, J=1.0, 2.7, 7.5 Hz, H-2),
4.05–4.10 (4H, m, H-6, H-6’), 3.62 (2H, ddd ꢁ dt J=3.8,
8.5 Hz, H-5), 2.14, 2.10, 1.97 (each s, each 6H, OAc);
13C NMR (CDCl3, 400 MHz, ppm): d=170.5, 169.5, 169.3 (C,
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À
C=O, Ac), 163.8 (C, O C=N), 147.0 (C, pyridine), 139.0 (CH,
pyridine), 128.0 (CH, pyridine), 100.3 (CH, C-1), 70.1 (CH,
C-5), 68.2 (CH, C-3), 68.0 (CH, C-4), 65.0 (CH, C-2), 62.5
(CH2, C-6), 20.8, 20.6, 20.5 (CH3, OAc); HR ESI-MS (posi-
tive):
m/z=728.1898, calcd. for C31H35N3O16 [M+Na]+:
G
728.2017; [a]: +92.72 (c 1.87, CHCl3).
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General Procedure for Cu(I)-Catalyzed Asymmetric
Alkynylation of Imines
The imines were synthesized by heating a mixture of freshly
distilled aldehyde (0.66 mmol) and amine (0.72 mmol) at
608C for about two hours. Under a nitrogen atmosphere
CuOTf·0.5C6H6 (5 mol%) and glucoPybox 4 (8 mol%) were
dissolved in dry dichloromethane (2–3 mL) and the alkyne
(0.99 mmol) was added. The preformed imine was slowly
added and the mixture was stirred at room temperature for
48 h. After completion of the reaction the solvent was re-
moved under vacuum. The residue was purified by flash chro-
matography on silica gel (petroleum ether/ethyl acetate, 33:1).
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Supporting Information
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Chem. Soc. 2007, 129, 5830–5831.
Full experimental procedures, characterisation data for all
compounds are available as Supporting Information.
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Díaz Gómez, J. Jios, C. O. Della VØdova, H. D. March,
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Acknowledgements
AHCTREUNG
We thank Deutsche Forschungsgemeinschaft, VW Stiftung
and Fonds der Chemischen Industrie for financial funding of
thiswork.
Adv. Synth. Catal. 2008, 350, 403 – 405
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