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CBS Catalysts

Aldrich ChemFiles 2005, 5.4, 2.

Aldrich ChemFiles 2005, 5.4, 2.

2-Methyl-CBS-oxazaborolidine and o-tolyl-CBS-oxazaborolidine

Since 1987, the series of chiral oxazoborolidines known as CBS catalysts (after Corey, Bakshi, and Shibata) have been used for catalytic reduction of prochiral ketones,1 imines,2 and oximes3 to produce chiral alcohols, amines, and amino alcohols, respectively, in excellent yields and ee’s. Sigma-Aldrich is pleased to offer both enantiomers of 2-methyl-CBS-oxazaborolidine as dry reagents, as well as 1 M solutions in toluene.

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

Scheme 1

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  1. (a) Corey, E. J. et al. 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, 3200.
  3. Tillyer, R. D. et al. Tetrahedron Lett. 1995, 36, 4337.
  4. Ryu, D. H.; Corey, E. J. J. Am. Chem. Soc. 2003, 125, 6388.

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