(R)-2-Methyl-CBS-oxazaborolidine explained

(R)-2-Methyl-CBS-oxazaborolidine is an organoboron catalyst that is used in organic synthesis. This catalyst, developed by Itsuno^{[1] [2]} and Elias James Corey,^{[3] [4] [5]} is generated by heating (R)-(+)-2-(diphenylhydroxymethyl) pyrrolidine along with trimethylboroxine or methylboronic acid. It is an excellent tool for the synthesis of alcohols in high enantiomeric ratio. Generally, 2-10 mol% of this catalyst is used along with borane-tetrahydrofuran (THF), borane-dimethylsulfide, borane-N,N-diethylaniline, or diborane as the borane source. Enantioselective reduction using chiral oxazaborolidine catalysts has been used in the synthesis of commercial drugs such as ezetimibe and aprepitant.

See also

• CBS catalyst
• Corey-Itsuno reduction

Notes and References

1. Hirao, A. . Itsuno, S. . Nakahama, S. . Yamazaki, N. . . Asymmetric reduction of aromatic ketones with chiral alkoxy-amineborane complexes . 1981 . 7 . 315–317 . 10.1039/C39810000315.
2. Itsuno, S. . Nakano, M. . Miyazaki, K. . Masuda, H. . Ito, K. . Hirao, A. . Nakahama, S. . . 1985 . 2039–2044 . 10.1039/p19850002039 . Asymmetric synthesis using chirally modified borohydrides. Part 3. Enantioselective reduction of ketones and oxime ethers with reagents prepared from borane and chiral amino alcohols.
3. Corey, E. J. . Bakshi, R. K. . Shibata, S. . . 1987 . 109 . 5551–5553 . 10.1021/ja00252a056 . Highly enantioselective borane reduction of ketones catalyzed by chiral oxazaborolidines. Mechanism and synthetic implications . 18.
4. Corey, E. J. . Bakshi, R. K. . Shibata, S. . Chen, C.-P. . Singh, V. K. . J. Am. Chem. Soc.. 1987 . 109 . 7925–7926 . 10.1021/ja00259a075 . A stable and easily prepared catalyst for the enantioselective reduction of ketones. Applications to multistep syntheses . 25.
5. Corey, E. J. . Azimioara, M. . Sarshar, S. . . 1992 . 33 . 3429–3430 . 10.1016/S0040-4039(00)92654-6 . X-Ray crystal structure of a chiral oxazaborolidine catalyst for enantioselective carbonyl reduction . 24. 97345807 .