有機催化硝基烯類化合物動力學分割-非掌性環己酮去對稱化反應之探討

Abstract

本研究在探討有機催化外消旋化合物動力學分割，並結合非掌性環己酮去對稱化反應，利用L-脯胺酸與樟腦架構的有機催化劑，先讓環己酮形成烯胺分子，烯胺分子與外消旋硝基烯類化合物反應，得到具有不錯產率(最高36%)及高鏡像選擇性(最高97% ee和 >99:1 dr)的產物，回收反應性較小的(R)-硝基烯類化合物，具有不錯的回收率及高光學純度(最高98% ee)。此反應經由SN2’的共軛加成-脫去反應，得到具三個掌性中心的產物分子，這是第一個成功以碳原子作為親核性試劑，同時進行動力學分割與去對稱化的例子。

An interesting organocatalytic kinetic resolution of racemic substances that combines desymmetrization of prochiral cyclohexanone was developed. The racemic nitroallylic acetates were readily resolved by prochiral cyclohexanones derived enamine by using pyrrolidine-linker-camphor based organocatalyst. The corresponding functionalized products were obtained with reasonable to good chemical yields and high to excellent levels of stereoselectivity (up to 36% yield and >99:1 dr, 97% ee). The less reactive (R)-nitroallylic acetates were obtained in good chemical yields and high optically purity (up to 98% ee). The reaction proceeded smoothly via conjugate addition and elimination sequences (an SN2’ process) by giving the products with to three stereogenic centers. This is the first example that carbon nucleophile was used for the kinetic resolution with simultaneous desymmetrization process.