doi:10.1016/j.tetlet.2005.09.065
Copyright © 2005 Elsevier Ltd All rights reserved.
Copper catalyzed tandem asymmetric conjugate addition–cyclization reaction in the presence of chiral phosphoramidite ligands
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Kangying Lia and Alexandre Alexakis
, a, 
aDepartment of Organic Chemistry, University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geveva, Switzerland
Received 25 July 2005;
revised 9 September 2005;
accepted 12 September 2005.
Available online 28 September 2005.
Abstract
Copper-catalyzed intramolecular conjugate addition–cyclization in the presence of chiral phosphoramidite ligands was described. Cyclic products with multiple chiral centers were obtained with up to 93:7 diastereomeric ratio and 94% ee.
Keywords: Copper; Tandem; Conjugate addition; Cyclization; Chiral; Phosphoramidite ligands
Table 1.
Results of conjugated addition–cyclization on substrate S1
a Determined by GC–MS.
b Ee measured by Chiral GC on the major diastereomer in parenthesis, ee of the minor one. Separation condition: Hydrodex-B-3P, 40 cm/s, 60-0-1-170-10,
T1 = 85.43 min,
T2 = 85.81 min,
T3 = 89.95 min,
T4 = 90.33 min.
c 76:24 ratio after isomerization using DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) in MeOH.
d Toluene used as solvent.
e Absolute configuration assigned by comparison with analogous adduct derived from
trans-3-nonen-2-one and Et
2Zn.
[2c] and [9]
Table 2.
Conjugated addition–cyclization on S2 with diethyl zinc
a Determined by GC–MS.
b Ee measured by SFC on the major diastereomer in parenthesis, ee of the minor one. Separation condition: Chiral OD-H, 200Bar, 2%-6-1-15%, 2 ml/min, 10 °C,
T1 = 3.93 min,
T2 = 4.12 min,
T3 = 4.49 min,
T4 = 4.83 min.
c Toluene used as solvent.
d 70:30 ratio after isomerization using DBU in MeOH.
e Absolute configuration assigned by comparison with analogous adduct derived from
trans-3-nonen-2-one and Et
2Zn.
[2c] and [9]
Table 3.
Conjugated addition–cyclization on substrate S3
a Determined by GC–MS.
b Ee measured by SFC on the major diastereomer in parenthesis, ee of the minor one. Separation condition: Hydrodex-B-3P, 30 cm/s, 60-0-1-170-10,
T1 = 78.33 min,
T2 = 79.48 min,
T3 = 85.48 min,
T4 = 86.27 min.
c Me
2Zn was used, toluene as solvent.
d Absolute configuration assigned by comparison with analogous adduct derived from
trans-3-nonen-2-one and Et
2Zn.
[2c] and [9]
Corresponding author. Fax: +41 22 379 6522.
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