Concerning kinetic resolution by the Sharpless asymmetric dihydroxylation reaction

Abstract

The transition state for the product-determining step in the Sharpless asymmetric dihydroxlation reaction is not product-like, and effective kinetic resolution can occur when one face of a chiral alkene is hindered.

References

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4. A value of 15.9 kJ mol^–1 was obtained by calculation. Gaussian 94 (revision C), Gaussian, Inc., Pittsburgh, PA., 1995.
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6. Diols 2 and 3 show CHOH resonances at δ4.02 (dd, J 11, 4 Hz) and 4.38 (m, width at half height < 10 Hz), respectively, in the ¹H NMR (after D₂O exchange). These diols have been prepared before in racemic form, see G. Berti, B. Macchia and F. Macchia, Tetrahedron, 1968, 24, 1755.
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8. Chiral shift reagent [Eu(tfc)₃] in 15% C₆D₆–CCl₄. Addition of 5% of the racemate was required before a discernible peak for the Bu^t protons' resonance of the minor enantiomer could be detected.
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11. Initially we synthesised (3RS,6RS)-3-tert-butyl-1,6-diphenylcyclohexene but it did not appear to undergo the AD reaction. This synthesis will be reported in the full paper.
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15. The radical inhibitor, 2,6-di-tert-butyl-p-cresol, was added during the work-up procedure, otherwise much lower yields of this alkene were obtained.
16. In the ¹H NMR spectrum, methoxy resonances at δ 3.37 and 3.53 for the diastereomers produced from the racemic diol showed separation at the base-line.