Effect of Fifth Coordination in Catalytic Epoxidation by a Chiral Manganese Porphyrin

Abstract

The effect of multifarious organic bases in chiral manganese porphyrin catalyzed enantioselective alkene epoxidation was investigated. For substituted pyridines, the enantioselectivity of cis-β-methylstyrene epoxidation follows a linear free energy relationship for pyridines bearing electron-donating groups. Compared to the case of no amine additive, a significant improvement in enantio­selectivity from 43% ee to 81% ee for epoxidation of cis-β-methylstyrene with a 86.5% stereospecificity were observed when DMAP and KHSO₅ were employed as axial ligand and oxidant respectively.

Key words

enantioselective epoxidation - metalloporphyrin - axial ligand - biomimetic oxidation

References

• 1a Casella L. Colonna S. In Metalloporphyrins Catalyzed Oxidations   Montanari F. Casella L. Kluwer Academic Publishers; New York: 1994. 
• 1b Auclair K. Moenne-Loccoz P. Ortiz de Montellano PR. J. Am. Chem. Soc.  2001,  123:  4877 
• 2 Jitsukawa K. Shiozaki H. Masuda H. Tetrahedron Lett.  2002,  43:  1491 
• 3 Collman JP. Brauman JI. Hampton PD. Tanka H. Bohle DS. Hembre RT. J. Am. Chem. Soc.  1990,  112:  7980 
• 4 Miura K. Katsuki T. Synlett  1999,  783 
• 5a Knoishi K. Oda K.-I. Nishida K. Aida T. Inoue S. J. Am. Chem. Soc.  1992,  114:  1313 
• 5b Collman JP. Lee VJ. Zhang X. Ibers JA. Brauman JI. J. Am. Chem. Soc.  1993,  115:  3834 
• 6 Collman JP. Lee VJ. Zhang X. Uffelman ES. Brauman JI. Science  1993,  261:  1404 
• 7 Daly AD. Renehan MF. Gilheany DG. Org. Lett.  2001,  3:  663 
• 8 Gross Z. Ini S. J. Org. Chem.  1997,  62:  5514 
• 9 Halterman RL. Jan S.-T. J. Org. Chem.  1991,  113:  6865 
• 10 Halterman RL. Jan S.-T. Abdulwali AH. Standlee DJ. Tetrahedron  1997,  53:  11277 
• 12 Palucki M. Finney NS. Pospisil PJ. Güler ML. Ishida T. Jacobsen EN. J. Am. Chem. Soc.  1998,  120:  948 
• 13a Jørgensen KA. Swanstrøm P. Acta Chem. Scand.  1988,  43:  822 
• 13b Gunter MJ. Turner R. J. Mol. Catal.  1991,  66:  121 
• 14 Berkessel A. Frauenkron M. J. Chem. Soc., Perkin Trans. 1  1997,  2265 

11

General procedure for catalytic oxidation: Oxone (8 mmol), NaHCO₃ (3.5 mmol), were dissolved in 4 mL deionized water with stirring. cis-β-Methylstyrene (8 mmol), catalyst 1 (0.0016 mmol), and axial ligand (0.008 mmol) were dissolved in acetonitrile (4 mL). The organic mixture was added to the aqueous mixture and the whole mixture was stirred overnight. The product mixture was extracted with diethyl ether four times and the combined extract was evaporated with a rotary evaporator. The product was analyzed by HP-6890 gas chromatography equipped with with a column, J&W Scientific cyclodex B column of 30 m length, 0.250 mm internal diameter, 0.25 µm film thickness.