New Lewis-basic N-oxides as chiral organocatalysts in asymmetric allylation of aldehydes.
Allylation of aromatic and heteroaromatic aldehydes 1a-k with allyltrichlorosilane 2 can be catalyzed by the new heterobidentate, terpene-derived bipyridine N-monoxides 4, 6a,b, and 8-11 (</=10 mol %) to afford (S)-(-)-3 with high enantioselectivities (</=99% ee). The stereochemical outcome has been found to be controlled by the axial chirality of the catalyst, which in turn is determined by the central chirality of the annulated terpene units. Solvent effects on the conversion and the level of asymmetric induction have been elucidated, and MeCN has been identified as the optimal solvent for these catalysts.
Malkov
Andrei V
AV
Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K.
Bell
Mark
M
Orsini
Monica
M
Pernazza
Daniele
D
Massa
Antonio
A
Herrmann
Pavel
P
Meghani
Premji
P
Kocovský
Pavel
P