新烯烃异构化催化剂
Metathesis reactions are finding greater use since the development of chiral catalysts that can metathesise functionalised olefins. Both ring-opening and ring-closing asymmetric reactions are known in which chiral catalysts are used. One drawback is that the catalysts are extremely air sensitive and hence require special handling techniques. It is also not always appreciated that the high sensitivity and reactivity of the catalysts means that high-purity starting materials are required. This patent discloses catalysts that are relatively stable and that can be recycled and reused. The main subject of the patent is the ruthenium complex 7 that is prepared by the route shown in Scheme 2. The amino alcohol is prepared in 98% yield by reductive amination involving pure 2 and aldehyde 3 in the presence of Na(OAc)3BH. The optically pure salt 6 is prepared in a two-step procedure and is obtained in 83% yield. Reaction of 6 with the Ru carbene complex 5 gives 7 that is purified by silica gel chromatography and isolated in 52% yield.
