3-HB(menthylpyrazolyl)3}Mg{1-OC(=CH2) cyclohexyl}
with 3,3-dimethyl-2-butanone3-HB(menthylpyrazolyl)3}Mg{1-OC(=CH2) cyclohexyl}
with 3,3-dimethyl-2-butanone3-HB(menthylpyrazolyl)3}Mg{1-OC(=CH2)cyclohxyl}
(0.10 g, 0.14 mmol) dissolved in Et2O (20 cm3) was prepared in a
reaction flask. 3,3-dimethyl-2-butanone (0.020 cm3, 0.16 mmol) was
added at -78oC. The mixture was warmed to -40 oC and
stirred for 7 h. The mixture was hydrolysed at 0oC with saturated
NH4Cl solution and the organic layer was separated and the aqueous layer
extracted with 3 x 20 cm3 Et2O. The organic extracts were combined
and dried with MgSO4. Solvent was removed under reduced pressure to leave a
yellow oil:G.C. [50 oC / inc.temp.2 oC / min / 200 oC (10 min)] (relative area) RT = 5.55 (CH3CH(CH3)2COCH3, 1), 15.70 (1.7), 25.79 (cyclohexylmethyl ketone, 10.2), 31.26/31.39 (ee = 26%, 2.01), 35.57 (CH3CH(CH3)2COCH2C(OH)(CH3)C(CH3)2CH3, 0.43 - trace isomer at 36.08), 38.01/38.15 (2.02), 58.00 (1.85), 66.42 (menthylpyrazole, 63.3) min.