Angewandte
Chemie
Sci. USA 2004, 101, 11960 – 11965. During preparation of this
Experimental Section
manuscript, the Ir-catalyzed asymmetric hydrogenation of N-
iminopyridinium ylides with high enantioselectivity was
reported: p) C. Y. Legault, A. B. Charette, J. Am. Chem. Soc.
2005, 127, 8966 – 8967.
In a glove box, THF (3 mL) was added to a mixture of [{IrCl(cod)}2]
(3.4 mg, 0.005 mmol) and (S)-segphos (6.8 mg, 0.011 mmol). Simi-
larly, THF (2 mL) was added to a mixture of Li2CO3 (79 mg,
1.2 mmol) and substrate 1a (1.0 mmol). Both mixtures were stirred
at room temperature for 10 min, then benzyl chloroformate
(1.1 mmol) was added to the solution of Li2CO3 and substrate.
Next, the in situ prepared catalyst solution was added with a syringe.
The hydrogenation was performed at room temperature under H2
(600 psi) for 12–15 h. After carefully releasing the hydrogen, the
reaction mixture was diluted with diethyl ether (20 mL), and
saturated sodium carbonate aqueous solution (10 mL) was added.
After stirring for 15 min, the aqueous layer was extracted with diethyl
ether (3 15 mL), dried over sodium sulfate, and concentrated to
afford the crude product 2a. Clean up was performed on a column of
silica gel eluted with hexane/EtOAc (10:1) to give the pure product.
The enantiomeric excesses were determined by chiral HPLC with AS-
H columns. Yield 90%, 90% ee, [a]8D = +105.2 (c = 0.98, CHCl3).
1H NMR (400 MHz, CDCl3): d = 1.18 (d, J = 6.4 Hz, 3H), 1.52 (m,
1H), 2.22 (m, 1H), 2.66 (m, 2H), 4.65 (m, 1H), 5.16, 5.29 (AB system,
J = 12.6 Hz, 2H), 7.02–7.15 (m, 3H), 7.31–7.37 (m, 5H), 7.56 ppm (d,
J = 8.0 Hz, 1H); 13C NMR (100 MHz, CDCl3): d = 20.2, 25.8, 31.7,
50.3, 68.0, 125.0, 126.1, 126.7, 128.4, 128.5, 128.6, 129.2, 132.5, 137.2,
155.3 ppm; HRMS for C18H20NO2 [M+1]: m/z calcd 282.1489, found
282.1476; HPLC (AS-H, eluent: hexane/iPrOH 95:5, detector:
254 nm, flow rate: 0.5 mLminÀ1): (S) t1 = 5.5 min, (R) t2 = 6.2 min.
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Received: August 29, 2005
Revised: November 21, 2005
Published online: March 3, 2006
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Keywords: asymmetric synthesis · chloroformates ·
enantioselectivity · hydrogenation · quinolines
.
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Angew. Chem. Int. Ed. 2006, 45, 2260 –2263
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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