Asymmetric diethyl- and diphenylzinc additions to aldehydes by using a fluorine-containing chiral amino alcohol: A striking temperature effect on the enantioselectivity, a minimal amino alcohol loading, and an efficient recycling of the amino alcohol
A chiral pyrrolidinylmethanol derivative containing perfluoro-ponytails (5) was prepared from (S)-proline. The use of this perfluoro-substituted amino alcohol in catalytic asymmetric additions of organozinc reagents to aldehydes affords products with high
Park, Jin Kyoon,Lee, Hong Geun,Bolm, Carsten,Kim, B. Moon
CBS reductions with a fluorous prolinol immobilized in a hydrofluoroether solvent
A fluorous prolinol precatalyst bearing only 34 fluorine atoms has been immobilized in the hydrofluoroether solvent HFE-7500. The CBS reduction of acetophenone proceeded rapidly, in high yield and in high ee in the absence of any organic solvent. The organic product was stripped from the HFE-7500 phase with a polar solvent, and the HFE-7500 phase was reused as is with satisfactory results through eight runs. This process is an attractive prototype for the large-scale use, recovery, and reuse of fluorous organocatalysts.
Chu, Qianli,Yu, Marvin S.,Curran, Dennis P.
supporting information; scheme or table
p. 749 - 752
(2009/04/06)
Enantioselective catalytic epoxidation of α,β-enones promoted by fluorous α,α-diaryl-l-prolinols
Enantioselective (up to 87% ee) epoxidation of a variety of α,β-enones to form α,β-epoxy ketones is described using a series of fluorous α,α-diaryl-l-prolinols as bifuncational organocatalysts and tert-butyl hydrogenperoxide (TBHP) as an oxidant.
Recoverable fluorous CBS methodology for asymmetric reduction of ketones
(Chemical Equation Presented) An operationally simple and recoverable fluorous CBS methodology was developed. The in situ-generated fluorous oxazaborolidine efficiently catalyzed the reduction of ketones with high enantioselectivity and reactivity. The subsequent recycling of the fluorous prolinol precatalyst was achieved by fluorous solid-phase extraction.
Dalicsek, Zoltan,Pollreisz, Ferenc,Goemoery, Agnes,Soos, Tibor
p. 3243 - 3246
(2007/10/03)
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