Chirality control by the aid of 2:2-dimethyloxazolidine chiral auxiliaries. Highly 1:4-chiral inductive asymmetric alkylations of amide enolates
作者:Shuji Kanemasa、Koichi Ueno、Kenjiro Onimura、Takashi Kikukawa、Hidetoshi Yamamoto
DOI:10.1016/0040-4020(95)00624-h
日期:1995.9
The propanamide and methoxyacetamide derivatives of (S)-4-benzyl-2,2,5,5-tetramethyloxazolidine, a new chirality controlling auxiliary based on the restricted rotation around amide bond, generate chiral lithium Z-enolates by lithiation. They undergo highly lk-1,4 and ul-1,4-inductive alkylations with a variety of alkylating reagents, respectively. The diastereotopic face participated in the reactions
(S)-4-苄基-2,2,5,5-四甲基恶唑烷的丙酰胺和甲氧基乙酰胺衍生物是一种新的手性控制助剂,其基于绕酰胺键的受限旋转,通过锂化生成手性Z-烯醇锂。它们分别通过各种烷基化试剂进行高度lk -1,4和ul -1,4-诱导烷基化。参与反应的非对映体面是在顺式构象中远离恶唑烷的4-保护取代基的面。过渡态的烯醇双键和恶唑烷平面之间的共面性可能是观察到的优异选择性的主要因素。