The Effect of Substituents on the Pyridine Ring in the Diastereoselective Cyclopropa- nation Reaction of Pyridinium Ylides Bear- ing an 8-Phenylmenthyl Ester Group
作者:Satoshi Kojima、Kouji Fujitomo、Yoshiaki Itoh、Kyoko Hiroike、Masaaki Murakami、Katsuo Ohkata
DOI:10.3987/com-05-s(t)56
日期:——
The reaction between β-substituted methylidenemalononitriles and the ylide from (-)-8-phenylmenthyl α-pyridiniumacetate, which affords activated cyclopropanes bearing two cyano groups and one carboxylic ester group, was examined. The trans isomer was obtained in up to 91:9 diastereoselectivity under optimized solvent conditions for the t-butyl substituted substrate. The selectivity increased to 96:4
研究了 β-取代的亚甲基丙二腈与 (-)-8-苯基薄荷基 α-吡啶鎓乙酸酯的内鎓盐之间的反应,得到带有两个氰基和一个羧酸酯基的活化环丙烷。在叔丁基取代底物的优化溶剂条件下,反式异构体的非对映选择性高达 91:9。使用 4-甲氧基吡啶代替吡啶时选择性增加到 96:4,而 N,N-二乙基烟酰胺的选择性通常较低。通过 X 射线结构分析确定主要的 4-吡啶基取代的环丙烷为反式 1R。