CBS Catalysts

2-Methyl-CBS-oxazaborolidines for asymmetric reduction

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 ketones^1-2, imines^3-5, and oximes⁶ to produce chiral alcohols, amines, and amino alcohols in excellent yields and ee’s. We are 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.

o-Tolyl-CBS-oxazaborolidines for asymmetric synthesis

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 No. 46463-5), these chiral oxazaborolidines generate chiral Lewis acids which have demonstrated great utility in the enantioselective Diels-Alder reaction (Scheme 1).⁷

Scheme 1. o tolyl cbs oxazaborolidine

References

1. Corey EJ, Bakshi RK, Shibata S. 1987. Highly enantioselective borane reduction of ketones catalyzed by chiral oxazaborolidines. Mechanism and synthetic implications. J. Am. Chem. Soc.. 109(18):5551-5553. https://doi.org/10.1021/ja00252a056

2. Corey EJ, Bakshi RK, Shibata S, Chen CP, Singh VK. 1987. A stable and easily prepared catalyst for the enantioselective reduction of ketones. Applications to multistep syntheses. J. Am. Chem. Soc.. 109(25):7925-7926. https://doi.org/10.1021/ja00259a075

3. Kirton EH, Tughan G, Morris RE, Field RA. 2004. Rationalising the effect of reducing agent on the oxazaborolidine-mediated asymmetric reduction of N-substituted imines. Tetrahedron Letters. 45(4):853-855. https://doi.org/10.1016/j.tetlet.2003.11.021

4. Cho BT, Chun YS. 1992. Enantioselective synthesis of optically active metolachlor via asymmetric reduction. Tetrahedron: Asymmetry. 3(3):337-340. https://doi.org/10.1016/s0957-4166(00)80268-2

5. Cho BT, Chun YS. Asymmetric reduction of N-substituted ketimines with the reagent prepared from borane and (S)-(?)-2-amino-3-methyl-1,1-diphenylbutan-1-ol (itsuno's reagent): enantioselective synthesis of optically active secondary amines. J. Chem. Soc., Perkin Trans. 1.(11):3200-3201. https://doi.org/10.1039/p19900003200

6. Tillyer RD, Boudreau C, Tschaen D, Dolling U, Reider PJ. 1995. Asymmetric reduction of keto oxime ethers using oxazaborolidine reagents. The enantioselective synthesis of cyclic amino alcohols. Tetrahedron Letters. 36(25):4337-4340. https://doi.org/10.1016/0040-4039(95)00788-e

7. Ryu DH, Corey EJ. 2003. Triflimide Activation of a Chiral Oxazaborolidine Leads to a More General Catalytic System for Enantioselective Diels?Alder Addition. J. Am. Chem. Soc.. 125(21):6388-6390. https://doi.org/10.1021/ja035393r