Mechanistic dichotomy in the asymmetric allylation of aldehydes with allyltrichlorosilanes catalyzed by chiral pyridine N-oxides
Detailed kinetic and computational investigation of the enantio- and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5, employing the pyridine N-oxides METHOX (9) and QUINOX (10) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate- and selectivity-determining step, which is supported by both experimental and computational data. Copyright
Malkov, Andrei V.,Stoncius, Sigitas,Bell, Mark,Castelluzzo, Fabiomassimo,Ramirez-Lopez, Pedro,Biedermannova, Lada,Langer, Vratislav,Rulisek, Lubomir,Kocovsky, Pavel
p. 9167 - 9185
(2013/07/26)
METHOX: A new pyridine N-oxide organocatalyst for the asymmetric allylation of aldehydes with allyltrichlorosilanes
(Chemical Equation Presented) Allylation of aromatic aldehydes with allyltrichlorosilane is catalyzed by the new terpene-derived pyridine N-oxide (+)-METHOX (≤5 mol %) in MeCN with high enantioselectivities (≤96% ee) and conversion rates; this catalyst re
Malkov, Andrei V.,Bell, Mark,Castelluzzo, Fabiomassimo,Kocovsky, Pavel
p. 3219 - 3222
(2007/10/03)
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