CBS Catalysts

Since 1987, the series of chiral oxazoborolidines known as CBS catalysts (after the work of Corey, Bakshi, and Shibata) have been used for catalytic reduction of prochiral ketones¹, imines², and oximes³ to produce chiral alcohols, amines, and amino alcohols in excellent yields and ee’s. Sigma-Aldrich is pleased to offer both enatiomers of 2-methyl-CBS-oxazaborolidine as a dry reagent, in addition to our current offerings as a 1M solution in toluene.

We are also pleased to offer the o-tolyl-CBS-oxazaborolidine as a 0.5M solution in toluene for your research needs. When protonated with trifluoromethanesulfonimide (product # 46463-5), these chiral oxazaborolidines generate chiral Lewis acids which have demonstrated great utility in the enantioselective Diels-Alder reaction (Scheme 1).⁴

References

1. (a) Corey, E. J.; Bakshi, R. K.; Shibata, S. J. Am. Chem. Soc. 1987, 109, 5551;
   (b) Corey, E. J. et al. ,J. Am. Chem. Soc.1987, 109, 7925.
2. (a) Kirton, E. H. M. et al. Tetrahedron Lett. 2004, 45, 853;
   (b) Cho, B. T.; Chun, Y. S. Tetrahedron: Asymmetry 1992, 3, 337;
   (c) Cho, B. T.; Chun, Y. S. J. Chem. Soc., Perkin Trans. 1 1990.
3. Tillyer, R. D. et al. Tetrahedron Lett. 1995, 36, 4337.
4. Ryu, D. H. and Corey, E. J. J. Am. Chem. Soc. 2003, 125, 6388.