Chlorodicyclohexylborane-mediated aldol additions of alpha,alpha'-dioxygenated ketones.
Boron aldol additions of variously O-protected alpha,alpha'-dioxygenated ketones using dicyclohexylboron chloride and a tertiary amine have been investigated. The stereoselectivity of the process was dependent on the protecting group on the alpha-oxygen atoms. Notably, ketones with bulky silyloxy groups gave syn aldols, most likely via Z enolates. This rules out the participation of chelates during the enolization process, at least in the presence of such sterically crowded protecting groups. An alternative explanation is offered.
Departamento de Q. Inorgánica y Orgánica, Universitat Jaume I, Castellón, E-12080 Castellón, Spain.
J
J
Murga
E
E
Falomir
M
M
Carda
F
F
González
J A
JA
Marco