Generation of α-boryl radicals by reduction of α-haloalkylboronic esters with CrCl2

Synlett

Volumn , Issue 3, 1998, Pages 253-254

  Takai, Kazuhiko ^a   Shinomiya, Norio ^a   Ohta, Masako ^a  

^a OKAYAMA UNIVERSITY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0009550749     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1998-1644     Document Type: Article

References (19)

1. Takai, K.; Matsukawa, N.; Takahashi, A.; Fujii, T. Angew. Chem., Int. Ed. Engl. 1998, 37, 152.
2. Nakatsukasa, S.; Takai, K.; Utimoto, K. J. Org. Chem. 1986, 51, 5045.
3. Takai, K.; Shinomiya, N.; Kaihara, H.; Yoshida, N.; Moriwake, T.; Utimoto, K. Synlett 1995, 963.
4. α-Chloroboronic esters were prepared by treatment of alkylboronic esters with lithium dichlorocarbenoid in 76-86% yields, according to the following procedure. Matteson, D. S.; Majumdar, D. Organometallics 1983, 2, 1529.
5. For reviews of α-halo boronic esters, see: Matteson, D. S. Chem. Rev. 1989, 89, 1535.
6. a) Batey, R. A.; Pedram, B.; Yong, K.; Baquer, G. Tetrahedron Lett. 1996, 37, 6847.
7. b) McCarroll, A.; Walton, J. C.; Nziengui, R.; Carboni, B. Chem. Commun. 1997, 2075.
8. For α-boryl alkylmetal compounds, see: a) Zn: Knochel, P. J. Am. Chem. Soc. 1990, 112, 7431.
9. b) Zr: Zheng, B.; Srebnik, M. J. Organomet. Chem. 1994, 474, 49.
10. For similar transformations via copper catalyzed 1,4-addition of α-boryl alkylzirconium compounds, see: Pereira, S.; Srebnik, M. Tetrahedron Lett. 1995, 36, 1805.
11. The reduction potential of the Cr(II)-Cr(III) couple in aqueous media is reported to be enhanced significantly by a complex formation with ethylenediamine. Kochi, J. K.; Singleton, D. M. J. Org. Chem. 1968, 33, 1027.
12. For some representative examples of α-oxyl radicals, see: Giese, B.; Engelbrecht, R.; Erfort, U. Chem. Ber. 1985, 118, 1289;
13. Protasiewicz, J.; Mendenhall, G. D. J. Org. Chem. 1985, 50, 3220;
14. Inanaga, J.; Otsubo, K.; Yamaguchi, M. Tetrahedron Lett. 1986, 27, 5763.
15. Starting α-halo boronic esters were prepared according to the following procedures, a) Brown, H. C.; Ravindran, N.; Kulkarni, S. U. J. Org. Chem. 1980, 45, 384.
16. b) Matteson, D. S.; Majundar, D. J. Organomet. Chem. 1979, 170, 259.
17. c) Phillion, D. P.; Neubauer, R.; Andrew, S. S. J. Org. Chem. 1986, 51, 1610.
18. d) Zeng, B.; Srebnik, M. Tetrahedron Lett. 1994, 35, 1145.
19. Chromium(II) chloride (>95% purity) was purchased from Aldrich Chemical Co.