有機催化連鎖反應與外消旋化合物之光學分割

Abstract

有機催化連鎖反應和光學分割結合是很有趣的反應類型。本實驗使用醋酸硝基丙烯酯外消旋混合物和戊二醛，以催化劑50催化，進行SN2’-Michael共軛加成-脫去連鎖反應，得到高立體選擇性四取代基環戊烯衍生物(高達96% ee 和12:1 dr)。回收反應性較低的起始物，同樣得到高光學純度(高達99% ee)。在文獻上，此反應是第一次利用不對稱有機催化經由SN2’-Michael共軛加成-脫去連鎖反應，合成高選擇性環戊烯衍生物，並且得到光學分割效率(s)高達143。The combination of organocatalytic cascade reaction and kinetic resolution is conceptually new in organocatalytic reaction. Treatment of racemic nitroallylic acetates 87 with glutaraldehyde 90 in the presence of a catalyst 50 to give tetrasubstituted cyclopentenes 118 with high to excellent stereoselectivities (up to 96% ee and 12:1 dr) via sequential SN2'-Michael process. The less reactive enantiomeric substrates were generally recovered with good to excellent optical purities (up to 99% ee). This is the first organocatalytic process for the synthesis of functionalized cyclopentenes with excellent stereoselectivities via an SN2′-Michael conjugate addition-elimination process. The selectivity factors (s) for the reaction ranged from 50 - 143.