Iron,Cobalt-Catalyzed Hydrosilylation Of Monosubstituted Alkenes

Silicon is the second most abundant element in the earth's crust after oxygen,and it is positioned just below carbon in the periodic table.Silicon formed silicates with oxygen and other elements,which occurs in nature as inorganic compounds.Carbon could form stable chemical bonds with itself and other elements in various forms,which is the basis of organic compounds.Organosilanes are compounds in which the silicon atom is attached to at least one carbon atom of organic groups.There are no natural organosilanes.Chemists created organosilanes by artificial synthesis,and found them having unique properties and wide applications.Chiral organosilanes have important potential applications in organic synthesis and silasubstitution in medicinal chemistry,while its synthetic methods are abundant.It is of great importances to develop precisive and efficient methods to construct chiral organosilanes.Transition metal-catalyzed asymmetric hydrosilylation of olefins is one of the most effective methods to construct chiral organosilanes.The precisive and efficient asymmetric hydrosilylation of olefins which using readily available monosubstituted olefins and hydrosilanes as starting materials,earth-abundant and biocompatible base metals as catalysts,is one of the most ideal methods to construct chiral organosilanes.However,due to the lack of suitable catalysts and catalytic systems,this field is still under-developed at present.In this paper,novel chiral imidazoline iminopyridine(IIP)and thiazoline iminopyridine(TIP)ligands which are suitable for iron and cobalt have been developed.Using the iron and cobalt complexes,we developed the dehydrogenative silylation and asymmetric hydrosilylation of monosubstituted olefins and obtained a series of useful vinylsilanes and chiral organosilanes.The research content of this paper is divided into the following parts:Part ?.The design and synthesis of IIP and TIP ligands.Novel IIP and TIP ligands were developed and applied in cobalt-catalyzed asymmetric sequential hydroboration/hydrogenation of internal alkynes and enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination,respectively.Part ?.Cobalt-catalyzed dehydrogenative silylation of monosubstituted vinylarenes.The imidazoline iminopyridine cobalt complexes could promote the dehydrogenative silylation of monosubstituted vinylarenes effectively and improve the chemoselectivities dramatically.The reaction could be carried out in gramscale and the proposed mechanism was also desribed.Part ?.Cobalt-catalyzed asymmetric hydrosilylation of monosubstituted olefins.Cobalt complexes with highly sterically hindered OIP ligands could effectively promote the asymmetric Markovnikov-type hydrosilylation of monosubstituted olefins.The functional group tolerability of this reaction was excellent.For aromatic olefins,enantioselectivities were all better than 98%ee.The method was also suitable for monosubstituted aliphatic olefins with enantioselectivities of 81-87%ee.Part ?.Iron-catalyzed asymmetric hydrosilylation of monosubstituted aliphatic olefins.Iron complexes with highly sterically hindered OIP ligands could effectively improve the regio-and enantioselectivities of asymmetric Markovnikov-type hydrosilylation of monosubstituted aliphatic olefins.The regio-and enantioselectivities of the reaction were better than 96/4 and 97%ee,respectively.Part ?.Experimental section.The general procedures of experiments and the characterization data of compounds in this dissertation were described.