Enantioselective Epoxidation of 2,2-Dimethylchromenes Using Achiral Mn-Salen Complex as a Catalyst in the Presence of Chiral Amine

Synlett

Volumn 1996, Issue 11, 1996, Pages 1079-1081

  Hashihayata, Takashi ^a   Ito, Yoshio ^a   Katsuki, Tsutomu ^a  

^a KYUSHU UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000899387     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1996-5695     Document Type: Article

References (18)

1. a) Katsuki, T. J. Synth. Org. Chem. Jpn. 1995, 53, 940.
2. b) Katsuki, T. Coord. Chem. Rev. 1995, 140, 189.
3. c) Jacobsen, E. N. In "Catalytic Asymmetric Synthesis" ed by I. Ojima, VCH publishers, Inc., New York, (1993), pp 159-202.
4. Srinivasan, K.; Michaud, P.; Kochi, J. K. J. Am. Chem. Soc. 1986, 108, 2309.
5. a) Hamada, T.; Fukuda, T.; Imanishi, H.; Katsuki, T. Tetrahedron 1996, 52, 515.
6. b) Norrby, P.-O.; Linde, C.; Åkermark, B. J. Am. Chem. Soc. 1995, 117, 11035.
7. Samsel, E.G.; Srinivasan, K.; Kochi, J. K. J. Am. Chem. Soc. 1985, 107, 7606.
8. For the effect of axial ligand on asymmetric induction in chiral Mn-salen catalyzed asymmetric epoxidation, see: Irie, R.; Ito, Y.; Katsuki, T. Synlett 1991, 265.
9. Another possibility is that the optically active donor ligand activates or deactivates one of two isomers (1 and ent-1) selectively. We can not exclude this possibility at present time.
10. a) Jacquier, R.; Maury, G. Bull. Chem. Soc. Fr. 1967, 295.
11. b) Brunner, H.; Scheck, T. Chem. Ber. 1992, 125, 701.
12. As for the determination of enantioselectivity, see the footnote c in Table 1.
13. A very useful list of chiral auxiliaries is available: Brunner, H.; Zettlemeier, W. "Handbook of Enantioselective Catalysis," VCH publishers, Inc., New York, (1993), Vol. 1 and 2.
14. Compound 11 was prepared from (-)-menthone in a conventional manner, unpublished results.
15. There is no possibility that the salen ligand is replaced with (-)-sparteine during the reaction and the resulting Mn-sparteine complex catalyzes epoxidation. Epoxidation using manganese(II) or manganese(III) acetate as a catalyst in the presence of excess (-)-sparteine did not occur.
16. The experiments were repeated and each value of ee's was reproduced in the error of 2%. (13) This observation is compatible with the mechanism involving a metallaoxetane intermediate (reference 3a). However, the present reaction conditions are very complex and we probably need more experiments before drawing conclusion on the meaning of non-linear relationship between ee and temperature in this reaction.
17. cis = 4.6 Hz. Enantioselectivity of the diols was determined by HPLC analysis using Daicel Chiralcel OBH (hexane/2-propanol 9:1). Enantioselectivity of 3,4-epoxy-2,2-dimethylchroman was determined by HPLC analysis using Daicel Chiralcel OD (hexane/2-propanol 15:1). Absolute configurations of the products were not determined.
18. No product other than the epoxide was detected by TLC analysis. In the epoxidation of 6-acetamido-7-nitro-2,2-dimethylchromene (Scheme 3), the unreacted starting material was recovered in 93% yield, after work-up.