Effects of Ligands and Additive Alcohols on Enantioselection in Highly Efficient Asymmetric Borohydride Reduction of Ketones Catalyzed by Optically Active Aldiminato Cobalt(II) Complexes

Synlett

Volumn 1996, Issue 11, 1996, Pages 1076-1078

  Nagata, Takushi ^a   Sugi, Kiyoaki D ^a   Yamada, Tohru ^a   Mukaiyama, Teruaki ^b  

^a MITSUI CHEMICALS INC   (Japan)

^b TOKYO UNIVERSITY OF SCIENCE   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0009283581     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1996-5693     Document Type: Article

References (18)

1. Nagata, T.; Yorozu, K.; Yamada, T.; Mukaiyama, T. Angew. Chem. 1995, 107, 2309; Angew. Chem. Int. Ed. Engl. 1995, 34, 2145.
2. Nagata, T.; Yorozu, K.; Yamada, T.; Mukaiyama, T. Angew. Chem. 1995, 107, 2309; Angew. Chem. Int. Ed. Engl. 1995, 34, 2145.
3. Sugi, K. D.; Nagata, T.; Yamada, T.; Mukaiyama, T. Chem. Lett. 1996, 737.
4. These ketones were purchased from Tokyo Kasei Kogyo Co., except 2 and 4 which were prepared by the literature methods: For 2, Garcia, J. G.; Enas, J. D.; Fronczek, F. R.; VanBrocklin, H. F. J. Org. Chem. 1994, 59, 8299; for 4, Bergmann, R.; Gericke, R. J. Med. Chem. 1990, 33, 492.
5. These ketones were purchased from Tokyo Kasei Kogyo Co., except 2 and 4 which were prepared by the literature methods: For 2, Garcia, J. G.; Enas, J. D.; Fronczek, F. R.; VanBrocklin, H. F. J. Org. Chem. 1994, 59, 8299; for 4, Bergmann, R.; Gericke, R. J. Med. Chem. 1990, 33, 492.
6. The absolute configurations were assigned by the polarimetry analysis. For 2, see Briaucourt, P.; Guetté, J.-P.; Horeau, A. C. R. Acad. Sci., Ser. C 1972, 274, 1203; for 3, see Wiedmann, R. ; Guetté, J.-P.; Normant, M. H. C. R. Acad. Sci., Ser. C 1969, 268, 2225; for 4, see Majeric, M.; Gelo-Pujic, M.; Sunjic, V.; Lévai, A.; Sebök, P.; Timar, T. Tetrahedron: Asymmetry 1995, 6, 937; for 5 and 6, see MacLeod, R.; Welch, F. J.; Mosher, H. S. J. Am. Chem. Soc. 1960, 82, 876.
7. The absolute configurations were assigned by the polarimetry analysis. For 2, see Briaucourt, P.; Guetté, J.-P.; Horeau, A. C. R. Acad. Sci., Ser. C 1972, 274, 1203; for 3, see Wiedmann, R. ; Guetté, J.-P.; Normant, M. H. C. R. Acad. Sci., Ser. C 1969, 268, 2225; for 4, see Majeric, M.; Gelo-Pujic, M.; Sunjic, V.; Lévai, A.; Sebök, P.; Timar, T. Tetrahedron: Asymmetry 1995, 6, 937; for 5 and 6, see MacLeod, R.; Welch, F. J.; Mosher, H. S. J. Am. Chem. Soc. 1960, 82, 876.
8. The absolute configurations were assigned by the polarimetry analysis. For 2, see Briaucourt, P.; Guetté, J.-P.; Horeau, A. C. R. Acad. Sci., Ser. C 1972, 274, 1203; for 3, see Wiedmann, R. ; Guetté, J.-P.; Normant, M. H. C. R. Acad. Sci., Ser. C 1969, 268, 2225; for 4, see Majeric, M.; Gelo-Pujic, M.; Sunjic, V.; Lévai, A.; Sebök, P.; Timar, T. Tetrahedron: Asymmetry 1995, 6, 937; for 5 and 6, see MacLeod, R.; Welch, F. J.; Mosher, H. S. J. Am. Chem. Soc. 1960, 82, 876.
9. The absolute configurations were assigned by the polarimetry analysis. For 2, see Briaucourt, P.; Guetté, J.-P.; Horeau, A. C. R. Acad. Sci., Ser. C 1972, 274, 1203; for 3, see Wiedmann, R. ; Guetté, J.-P.; Normant, M. H. C. R. Acad. Sci., Ser. C 1969, 268, 2225; for 4, see Majeric, M.; Gelo-Pujic, M.; Sunjic, V.; Lévai, A.; Sebök, P.; Timar, T. Tetrahedron: Asymmetry 1995, 6, 937; for 5 and 6, see MacLeod, R.; Welch, F. J.; Mosher, H. S. J. Am. Chem. Soc. 1960, 82, 876.
10. 3 (2.5 ml each) were successively added, and the mixture was continued to stir for 12 h at -20°C. The mixture was quenched by the addition of saturated aqueous ammonium chloride, and extracted with diethyl ether. The combined organic layers were washed with brine and dried over anhydrous sodium sulfate, and then the excess solvents were removed under reduced pressure. The purification by column chromatography on silica gel (hexane/ethyl acetate) gave the corresponding alcohol in 96% yield (84 mg). The optical purity was determined by using Daicel Chiralcel OD-H (hexane/2-propanol).
11. 2)) was determined as (S,S) by X-ray analysis of the corresponding cobalt(III) complex; unpublished results. SHELXL-93 program was used; Flack, H. D. Acta Cryst. 1983, A39, 876.
12. 2)) was determined as (S,S) by X-ray analysis of the corresponding cobalt(III) complex; unpublished results. SHELXL-93 program was used; Flack, H. D. Acta Cryst. 1983, A39, 876.
13. The combined use of 1-propanol, 2-propanol, or 2-methyl-2-propanol with THFA for the modification of borohydride was not apparently effective in the present procedure compared with ethanol; following results were obtained in the reduction of ketone 6; 88% ee with 1-propanol, 84% ee with 2-propanol, and 83% ee with 2-methyl-2-propanol, respectively. When 1-propanol and THFA were used together in the reduction, following results were observed; 88% ee for 6, 89% ee for 7, 40% ee for 8, and 37% ee for 5, respectively. High enantioselection would be achieved by the optimal matching of the alcohols.
14. Detailed examinations of the modified borohydride with alcohols will be published.
15. Aldiminato cobalt(III) complex was used for the crystallographical analysis instead of the cobalt(II) complex. It was confirmed that the cobalt(III) complex could be similarly employed as the corresponding cobalt(II) complex.
16. Aldiminato manganese(III) complex was found to have similar molecular structures as this cobalt(III) complex; Nagata, T.; Imagawa, K.; Yamada, T.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1995, 68, 3241.
17. 4 revealed that the source of hydride was not additive alcohols but borohydride.
18. Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525.