- Asymmetric synthesis of (diene)Fe(CO)3 complexes by a catalytic enantioselective alkylation using dialkylzincs
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The reaction of meso-(2,4-hexadien-1,6-dial)Fe(CO)3 complex 1 with several alkylzincs in the presence of 50 mol% of (S)-(+)diphenyl(1- methylpyrrolidin-2-yl)methanol 6a proceeded with high enantiotopic group- and diastereotopic face-selectivity to give (2R,6S)-alcohol complexes 2a-c as major products, except in the case with dimethylzinc (>90% de and >98% ee). On the otherhand, the methylation of 1 with Me2Zn proceeded with high enantioselectivity by adding 1.8 equiv. of Ti(Oi-Pr)4 in the presence of 3 tool% of (S,S)- 1,2-bis(trifluoromethylsulfonamide)cyclohexane 9a (82% de, 96% ee). The enantioselective alkylation was also applied to the kinetic resolution of racemic (sorbic aldehyde)Fe(CO)3 complex 10.
- Takemoto, Yoshiji,Baba, Yasutaka,Honda, Asami,Nakao, Syusuke,Noguchi, Izumi,Iwata, Chuzo,Tanaka, Tetsuaki,Ibuka, Toshiro
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- Lanthanide Lewis acid-mediated enantioselective conjugate radical additions
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(figure presented) Lanthanide triflates along with proline-derived ligands have been found to be efficient catalysts for enantioselective conjugate addition of nucleophilic radicals to enoates. N-Acyl oxazolidinones, when used as achiral additives, gave meaningful enhancements in the ees for the product.
- Sibi, Mukund P.,Manyem, Shankar
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p. 2929 - 2932
(2007/10/03)
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