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.
研究了使用二环己基
氯化
硼和叔胺加成各种O保护的α,α'-二加氧酮的
硼醇醛。该方法的立体选择性取决于α-氧原子上的保护基。值得注意的是,带有庞大甲
硅烷基氧基的酮很可能通过Z烯醇盐生成顺式羟醛。至少在空间上拥挤的保护基团存在的情况下,这排除了螯合过程中螯合物的参与。提供了另一种解释。