Stereoselective synthesis of both syn- and anti-N-tert-alkylamines using highly stereospecific crotylation of ketone-derived acylhydrazones with crotyltrichlorosilanes.
Crotyltrichlorosilanes reacted with ketone-derived N-benzoylhydrazones in DMF without any catalyst. This is the first example of highly stereospecific crotylation of ketimine analogues leading to both syn- and anti-N'-tert-alkyl-N-benzoylhydrazines. Different reactivities between (Z)- and (E)-crotylsilanes in terms of yields and selectivities were observed. A kinetic study with both geometrically pure (Z)- and (E)-crotylsilanes was performed. These reactions are most likely to proceed via a cyclic chairlike transition state where the aromatic group of hydrazones takes an axial position. Both diastereomers of allylation products can be converted to the corresponding alpha,alpha-disubstituted homoallylic amines without epimerization.
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Chikako
C
Ogawa
Masaharu
M
Sugiura
Shū
S
Kobayashi