Copper-Catalyzed Asymmetric 1,4-Silylation/Borylation Of Conjugated Enynes

Axial chiral allenes widely exist in natural products,pharmaceutical molecules and functional organic materials.Because of their unique reactivity,they have become important synthetic blocks in organic synthesis.In the past few decades,continuous efforts have been devoted to their asymmetric synthesis.Among them,the 1,4functionalization of conjugated enynes was an efficient pathway to obtain chiral allenes.On the other hand,due to the various transformations of organosilicon/boron compounds,the synthesis of multifunctional chiral allene derivatives containing silyl/boryl has attracted widespread attention.In this dissertation,we developed a series of methods for the synthesis of homoallenylsilanes/homoallenylboronates by using different 1,3-conjugated enynes as starting materials via copper-catalyzed nucleophilic addition and radical addition,respectively.The research work mainly included the following three parts:Part Ⅰ:Copper-catalyzed Stereo-selective 1,4-Protosilylation of Alkynylsubstituted Enones.In this work,we developed a reliable method for the synthesis of the enantioenriched homoallenylsilanes via copper-catalyzed asymmetric 1,4protosilylation of alkynyl-substituted enones with silylboronate.This novel transformation was featured by its good enantioselectivity,diastereoselectivity and excellent functional group tolerance under mild reaction conditions.This work offered a straightforward approach for the synthesis of the functional homoallenylsilanes with contiguous axial and central chirality,which also provided a feasibility to synthesize chiral allenes containing multi-stereocenters by silicon-heteroatom addition of 1,3enynes.Moreover,the corresponding products were effective synthons for the preparation of useful chiral furan derivatives.Part Ⅱ:Copper-catalyzed 1,4-Protosilylation/Protoborylation of Enynic Orthoesters.Herein,we reported a copper-catalyzed 1,4-protosilylation-hydrolyzation and 1,4protoborylation-hydrolyzation of enynic orthoesters.The enynic orthoesters as precursors of unstable enynic esters were applied to produce the functionalized 2,3allenoate products.This method provided a convenient and efficient methodology for the synthesis of functionalized homoallenylsilanes and homoallenylboronates.Meanwhile,we realized the synthesis of allenoates in one-pot.Additionally,the asymmetric 1,4-protosilylation-hydrolyzation of enynic orthoesters with PhMe2Si-Bpin was also successfully achieved.The newly synthesized chiral monopyridine imidazoline ligand was crucial for maintaining the reactivity and good enantioselectivity of the asymmetric 1,4-protosilylation.Part III:Copper-catalyzed 1,4-Cyanosilylation of Unactivated Conjugated Enynes.In this work,we developed a 1,4-cyanosilylation of unactivated conjugated enynes via a silicon radical pathway.Under simple reaction conditions,various tri-and tetrasubstituted homoallenylsilane products could be obtained in high yields by using trace amount of cheap copper as catalyst.In addition,a wide range of functional groups were compatible.