Molybdenum chloride catalysts for Z-selective olefin metathesis reactions

摘要

Development of catalyst-controlled stereoselective olefin metathesis processes has been a pivotal recent advance in chemistry. Incorporation of appropriate ligands within molybdenum-, tungsten and ruthenium-based complexes has made reactivity and selectivity levels that were formerly inaccessible feasible. Here, we show that molybdenum monoaryloxide chloride (MAC) complexes furnish higher energy (Z) isomers of trifluoromethyl-substituted alkenes through cross-metathesis (CM) reactions with commercially available, inexpensive and typically inert Z-1,1,1,4,4,4-hexafluoro-2-butene. Furthermore, otherwise inefficient and non-stereoselective transformations with Z-1,2-dichloro- and 1,2- dibromoethene can be effected with substantially improved efficiency and Z selectivity. Synthesis of representative biologically active molecules and trifluoromethyl analogues of medicinally relevant compounds underscore the importance of the advance. The origins of activity and selectivity levels, which contradict the previously proposed principles, are elucidated with the aid of DFT calculations.