(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 checkY
    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:
GHS02: FlammableGHS05: CorrosiveGHS07: Exclamation markGHS08: Health hazard
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).
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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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