(R)-2-Methyl-CBS-oxazaborolidine

(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.

(R)-2-Methyl-CBS-oxazaborolidine
Names
Preferred IUPAC name
(3aR)-1-Methyl-3,3-diphenyltetrahydro-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole
Other names
(R)-Methyl oxazaborolidine; (R)-(+)-2-methyl-CBS-oxazaborolidine
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.103.901
EC Number
  • 601-151-0
  • InChI=1S/C18H20BNO/c1-19-20-14-8-13-17(20)18(21-19,15-9-4-2-5-10-15)16-11-6-3-7-12-16/h2-7,9-12,17H,8,13-14H2,1H3/t17-/m1/s1 Y
    Key: VCDGSBJCRYTLNU-AZWGFFAPSA-N N
  • InChI=1/C18H20BNO/c1-19-20-14-8-13-17(20)18(21-19,15-9-4-2-5-10-15)16-11-6-3-7-12-16/h2-7,9-12,17H,8,13-14H2,1H3/t17-/m1/s1
    Key: VCDGSBJCRYTLNU-AZWGFFAPBY
  • O2B(N1CCC[C@@H]1C2(c3ccccc3)c4ccccc4)C
Properties
C18H20BNO
Molar mass 277.17 g·mol−1
Appearance Colorless to pale yellow liquid (in toluene)
Density 0.95 g/mL
Melting point 85 to 95 °C (185 to 203 °F; 358 to 368 K)
Boiling point 111 °C (232 °F; 384 K)
Hazards
GHS labelling:
Danger
H224, H225, H302, H304, H315, H318, H319, H332, H335, H336, H361, H373
P201, P202, P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P281, P301+P310, P301+P312, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P308+P313, P310, P312, P314, P321, P330, P331, P332+P313, P337+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

See also

References
  1. Hirao, A.; Itsuno, S.; Nakahama, S.; Yamazaki, N. (1981). "Asymmetric reduction of aromatic ketones with chiral alkoxy-amineborane complexes". J. Chem. Soc. Chem. Commun. (7): 315–317. doi:10.1039/C39810000315.
  2. Itsuno, S.; Nakano,M.; Miyazaki, K.; Masuda, H.; Ito, K.; Hirao, A.; Nakahama, S. (1985). "Asymmetric synthesis using chirally modified borohydrides. Part 3. Enantioselective reduction of ketones and oxime ethers with reagents prepared from borane and chiral amino alcohols". J. Chem. Soc. Perkin Trans. 1: 2039–2044. doi:10.1039/p19850002039.
  3. Corey, E. J.; Bakshi, R. K.; 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. doi:10.1021/ja00252a056.
  4. Corey, E. J.; Bakshi, R. K.; Shibata, S.; Chen, C.-P.; Singh, V. K. (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. doi:10.1021/ja00259a075.
  5. Corey, E. J.; Azimioara,M.; Sarshar, S. (1992). "X-Ray crystal structure of a chiral oxazaborolidine catalyst for enantioselective carbonyl reduction". Tetrahedron Lett. 33 (24): 3429–3430. doi:10.1016/S0040-4039(00)92654-6.
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