Selective Hydrosilation Of Allyllic Azide Compounds

The allylic azide is one type of unique azide compounds.Usually there are three existing isomers,one of which is with terminal azido group and the trans/cis-internal double bond,and the other is with the internal azido group and terminal double bond.And they can undergo the[3,3]rearrangement at room temperature to achieve the inter?converting equilibrium between them.The application of allylic azides in the organic synthesis is greatly limited by the presence of the mixture.In this thesis,the different rate of monosubstituted olefins and 1,2-disubstituted olefins in the hydrosilation reaction is utilized.The isomer with the internal azide and terminal double bond reacts faster in the hydrosilylation reaction than the isomer with the internal double bond under the employment of the platinum catalyst.But the isomer with the internal double bond can occur in the[3,3]rearrangement to afford the other isomer,and then further undergoes a hydrosilation reaction to selectively afford the sole hydrosilation product.In this thesis,four methods for the synthesis of allylic azides were studied,and the industrially used Karstedt's catalyst was selected,and finally a simple and efficient method is obtained for the selective hydrosilation of allylic azides.This thesis is divided into four parts:1.Synthesis of allyllic azides.In this chapter,four methods are explored for the synthesis of aliphatic,aromatic,epoxy allylic azide mixtures with different fonctional groups.The first method is a substitution reaction of an alcohol.First,the substituted allyllic alcohol reacted with carbon tetrabromide under the action of triphenylphosphine to form the allyllic bromide,and then substituted with sodium azide to give the product.The second method is a cross-coupling reaction of olefins.A terminal olefin having different functional groups was coupled with allyl bromide by an olefin cross-coupling catalyst HG-2,and then reacted with sodium azide to give the desired product.The third method is the derivatization of a mixture of allyllic azides.Modification of the synthetic allyl azide mixture gave a new mixture of allyllic azides.The fourth method is a 1,4-dibromobutene-mediated synthesis of a mixture of allyllic azides.A substitution reaction of 1,4-dibromobutene is first earied out with a substrate having a nucleophilic group,and reacted with sodium nitride.Through the above four methods,we prepared 30 allylic azide mixtures,which cover aliphatic,aromatic,epoxy,aldehyde,ketone,ester,amide and other functional groups,in order to explore the compatibility of hydrosilation reaction.2.Condition screening for the hydrosilation of allyllic azides.We used phenyldimethylsilane as a silicane source to screen the catalysts with different metals,and finally determined the industrially used Karstedt's catalyst as the best catalyst.Then the conditions were explored and we screened reaction solvent,amount of silane,reaction temperature,amount of catalyst and reaction time.The optimal reaction condition for selective hydrosilation of allyllic azides were determined to be Karstedt's catalyst.(0.5 mmol%),dimethylphenylsilane(4 equiv)in toluene at 60? for 24 h.3.Substrate expansion of the selective hydrosilation reaction of the allyllic azides.Under our optimal conditions,the allylic azides with different functional groups undergo the selective hydrosilation reaction with phenyl aimethylsilane.We totally obtained 26 new compounds with the yield of 70-80%,and the structure was verified by NMR,HRMS,and other methods.These results indicate that this method is with good selectivity for the hydrosilation reaction of the allyllic azides.4.Derivatization of hydrosilation products.Based on the above studies,we tried to optimize the reaction conditions with different silanes such as tert-butyldimethylsilane,triethoxysilane,triphenylsilane,and other silanes,with the yield of 70-85%.In addition,in this chapter we also explore the conditions of silane oxidation by controlling the amount of tetrafluoroboric acid,and it can selectively give the product of alcohol or ketone.