Selective Hydroboration Of Equilibrating Allyliclic Azides

Allylic azide is a special type of nitrogen-containing organic compounds,which often exist in the form of a mixture.Under normal circumstances,they have three isomers,namely,the cis/trans isomer of olefin in the middle and the isomer of olefin at the end.Meanwhile,these three isomers can rearrange by themselves at room temperature.This greatly limits the use of allylic azides in organic synthesis.In this thesis,the reaction rate of allylic azide isomers is different in the hydroboration reaction,so that the hydroboration reaction takes place in the terminal isomer of olefin,while the other two isomers almost do not react.But,they can rearrange to the isomer with olefin at the terminal,so that there is only one hydroboration product selectively This thesis is mainly divided into three parts:1.Condition screening for the hydroboration of allylic azide mixtures.We selected different metal catalysts using pinacolborane as boron source,and finally decided to use iridium metal catalyst.Then the ligand,additive,modified IrCOCl(PPh3)2 series catalyst,solvent,the amount of pinacolborane,temperature,the amount of catalyst,addition order and other factors were screened.Finally,the optimal reaction conditions for selective hydroboration of allylic azide mixture were determined as follows:IrCOCl(PPh3)2 as catalyst with 5 mol%of the optimal amount,the dosage of pinacolborane as 4.0 equiv.,reaction temperature as 90℃,reaction time as 20 h.Under these conditions,the ratio of by-products in hydroboronization of allylic azide mixture is the lowest and the yield is acceptable.2.Substrate expansion for selective hydroboration of allylic azide mixtures.The first part is the synthesis of allylic azide mixtures.This thesis mainly explores three methods to synthesize aromatic groups,nitrogen heterocycles and allylic azide mixtures with different functional groups.We have prepared 20 alyllic azide mixtures.Under the optimized conditions,we used allylic azide mixture with different functional groups to conduct the selective hydroboration with pinacolborane,and finally successfully prepared 23 hydroboration products with the yield of 44～82%.Their structures were confirmed by NMR,HRMS,IR and other methods.The results show that the hydroboration of allylic azide mixtures has good selectivity and compatibility.3.The derivatization of hydroboration products and initial exploration of hydroboration mechanism.We carried out derivatization reaction of boronate and converted boronate into hydroxyl,vinyl,furan,anisole and other functional groups.We also made an initial exploration on the mechanism of hydroboration of allylic azide mixture,and speculated a possible mechanism:iridium catalyst first formed Ir-B bond with boronate,and then reacted with terminal olefin isomer in the allylic azide mixture,metal iridium coordinated with olefin,then oxidative addition occurred,and then metal elimination occurred to obtain hydroboration product.