Y. Takemoto et al., Asymmetric synthesis of (diene)Fe(CO)(3) complexes by a catalytic enantioselective alkylation using dialkylzincs, TETRAHEDRON, 54(51), 1998, pp. 15567-15580
The reaction of meso-(2,4-hexadien-1,6-dial)Fe(CO)(3) complex 1 with severa
l alkylzincs in the presence of 50 mol% of (S)-(+)- diphenyl(diphenyl(1-met
hylpyrrolidin-2-yl)methanol 6a proceeded with high enantiotopic group- and
diastereotopic Face-selectivity to give (2R,6S)-alcohol complexes 2a-c as m
ajor products, except in the case with dimethylzinc (>90% de and >98% ee).
On the other hand, the methylation of 1 with Me2Zn proceeded with high enan
tioselectivity by adding 1.8 equiv. of Ti(Oi-Pr)(4) in the presence of 3 mo
l% of (S,S)-1,2-bis(trifluoromethylsulfonamide)cyclohexane 9a (82% de, 96%
ee). The enantioselective alkylation was also applied to the kinetic resolu
tion of racemic (sorbic aldehyde)Fe(CO)(3) complex 10. (C) 1998 Elsevier Sc
ience Ltd. All rights reserved.