A highly efficient, Z-selective ring-closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium-based catalyst supported by a dithiolate ligand is reported. This catalyst is demonstrated to be remarkably active as observed in initiation experiments showing complete catalyst initiation at - 20°C within 10 min. Using easily accessible diene starting materials bearing a Z-olefin moiety, macrocyclization reactions generated products with significantly higher Z-selectivity in appreciably shorter reaction times, in higher yield, and with much lower catalyst loadings than in previously reported systems. Macrocyclic lactones ranging in size from twelve-mem bered to seventeen-membered rings are synthesized in moderate to high yields (68 - 79% yield) with excellent Z-selectivity (95% - 99% Z).
报道了一种高效的、Z-选择性的环闭合交换反应系统,利用一种具有立体保留性的二
硫醇
配体支持的基于
钌的催化剂形成大环分子。该催化剂在引发实验中表现出非常高的活性,在-20℃下10分钟内完全引发。使用易得的含有Z-烯烃基团的二烯起始物,大环化反应生成的产物具有明显更高的Z-选择性,反应时间明显缩短,产率更高,催化剂负载量比先前报道的系统低得多。合成了大小从十二元环到十七元环的大环内酯,收率为中等到高收率(68-79%),Z-选择性优异(95%-99% Z)。