Mechanism Of Rhodium-Catalyzed Ligand Controlling Regional Selectivity Of Cyclopropene Hydromercaptan Reaction

The C-S bond exists in many important biological and pharmaceutical compounds,so the development of mild and efficient C-S bond construction methods has attracted extensive attention.Among the many compounds containing C-S,cyclopropyl and allyl sulfides and their derivatives are also natural products with a wide range of biological activities.In terms of synthesis,hydrogen-mercaptan catalyzed by transition metal represents an efficient and atom-economical method for alkenes.However,there are still many problems in the formation of C-S bonds by transition metal-catalyzed hydromerethiolation: for example,the region of reaction and the mechanism of stereoselectivity are not clear.Therefore,this paper mainly studied the reaction mechanism of rhodium-catalyzed ligand controlling the region and stereoselectivity of cyclopropene hydromerthiol by DFT.The main contents include the following three parts:(1)The research development and current situation of transition metal-catalyzed hydromerthiol reaction and transition metal-catalyzed cyclopropene ring-opening reaction;And the application of DFT calculation in transition metal catalyzed hydromercaptan reaction.(2)According to the rhodium-catalyzed hydromercaptan reaction of cyclopropene controlled by ligand,the origin of the chemical selectivity controlled by ligand was found.The mechanism of regional and stereoselectivity of the reaction;Therefore,we used the DFT to carry out ring-opening and ring-retaining studies under different ligands.It was found by comparison that under the condition of Josiphos ligand(L5),cyclopropylene was firstly oxidized by addition,then hydrogen transfer was carried out by insertion of Rh-H bond,and finally,direct reduction was eliminated to obtain environment-friendly residual products.Under the condition of DTBM-BINAP ligand(L8),cyclopropene is firstly oxidized,then inserted into Rh-H bond for hydrogen transfer,then formed by rh-π-allyl complex through ring-opening,and finally eliminated by reduction to produce ring-opening products.The steps that determine the reaction rate and regional selectivity are cyclopropene insertion into Rh-H bond.(3)According to the above results,the steric hindrance,electron effect and bite Angle effect caused by the bisphosphine ligand-rhodium system were analyzed.It was found that in the ring retention reaction,the rhodium catalyst with a small complex bite Angle and an electron-rich Josiphos ligand(L5)promoted the reduction elimination and formed the C-S bond of cyclopropyl sulfide product.For the ring-opening reaction,the rhodium catalyst of the DTBM-BINAP ligand(L8),which complexed the larger occlusal Angle ligand,promoted the ring-opening reaction,resulting in cyclopropane ring isomerization to produce allyl sulfide.Among them,bisphosphonate ligand adjusts the bite Angle of P-Rh-P by adjusting the spatial position of its substituents,and also influences and controls the reaction region and enantioselectivity through various electronic effects.The mechanism analysis of this study is expected to provide new insights into the involvement of transition metals in hydromercaptan and the different hydrofunctionalization reactions of cyclopropene with a wide range of nucleophiles.