Abstract
Purchase PDF (201 K)
E-mail Article
Add to my Quick Links
Cited By in Scopus (1)
Purchase PDF (337 K)
25, at 20 °C) and a minimum (
doi:10.1016/j.tet.2007.03.032 
Copyright © 2007 Elsevier Ltd All rights reserved.
Kinetic resolution of 5-substituted cycloalkenones by peptidic amidophosphane-copper-catalyzed asymmetric conjugate addition of dialkylzinc
Received 14 January 2007;
References and further reading may be available for this article. To view references and further reading you must purchase this article.
Abstract
Asymmetric conjugate alkylation reaction of racemic 5-substituted cyclohexenones with dialkylzinc reagents was catalyzed by 2–5 mol % of dipeptidic amidophosphane-Cu(MeCN)4BF4 in toluene at 0 °C for 20 min to recover enantioenriched starting 5-substituted cyclohexenones with 88–98% ee in 28–41% yield along with trans major 3-alkylated 5-substituted cyclohexanones with 81–90% ee in 53–60% yield. Complete consumption of starting racemic 5-TMS-cyclohexenone by treating with diethylzinc under the catalytic asymmetric reaction conditions gave trans major 85:15 mixture of trans- and cis-3-ethyl-5-TMS-cyclohexanones with 15% ee (for trans) in 83% combined yield, indicating that the conformation-controlled trans-alkylation of cyclohexenone prevails over chiral catalyst-controlled enantiofacial differentiation.
Article Outline
- 1. Introduction
- 2. Results and discussion
- 2.1. Catalytic kinetic resolution of 5-substituted cyclohexenones
- 2.2. Enantiofacial selection by chiral catalyst control versus trans-alkylation by substrate control
- 3. Conclusion
- 4. Experimental
- 4.1. General
- 4.1.1. Kinetic resolution of racemic 5-trimethylsilylcyclohexenone 11a (R1=TMS) to (−)-(R)-12a (R1=TMS) with diethylzinc (Table 1, entry 1)
- 4.1.2. (−)-3-Isopropyl-5-trimethylsilylcyclohexanone 13 (R1=TMS, R2=i-Pr) (entry 2)
- 4.1.3. (−)-(R)-5-Methylcyclohexenone 12b (R1=Me) (entry 3)
- 4.1.4. (−)-(R)-5-Phenylcyclohexenone 12c (R1=Ph) (entry 4)
- 4.1.5. (−)-(R)-5-(Naphth-2-yl)cyclohexenone 12d (R1=2-naph) (entry 5)
- Acknowledgements
- References
