Merck

CBS Catalysts

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,2-4 and oximes5 to produce chiral alcohols, amines, and amino alcohols, respectively, in excellent yields and ee’s. We are 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)6.

Diels–Alder reaction

Scheme 1.Diels–Alder reaction

Materials
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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. http://dx.doi.org/10.1021/ja00252a056
2.
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. http://dx.doi.org/10.1016/j.tetlet.2003.11.021
3.
Cho BT, Chun YS. 1992. Enantioselective synthesis of optically active metolachlor via asymmetric reduction. Tetrahedron: Asymmetry. 3(3):337-340. http://dx.doi.org/10.1016/s0957-4166(00)80268-2
4.
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. http://dx.doi.org/10.1039/p19900003200
5.
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. http://dx.doi.org/10.1016/0040-4039(95)00788-e
6.
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. http://dx.doi.org/10.1021/ja035393r