Iridium(III)-Catalyzed Direct C(sp2)-and C(sp~3)-H Alkynylation of 2-Acyl Imidazoles

摘要

Metal catalyzed C-H functionalization reactions have created noteworthy evolvement for lasttwo decades due to its effective and straight forward approaches for commencing a functionalgroup.Alkynes are among the most unique functional groups and are broadly present in naturalproducts,drugs,and organic materials.It also permits to host of a spacious range of C-C/or Cheteroatom centered functional groups which can easily reassigned into different carbo-/heterocycles with distinct ring size.However,there are many literatures available for directedC-H alkynylation,but most of previous studies focused on C(sp~2)-H alkynylation and fewexamples are available on C(sp~3)-H alkynylation.Herein,we report C(sp~2)-and C(sp~3)-Halkynylation of 2-acyl imidazole derivatives by iridium catalyst with a variety of bromoalkynesin good to excellent yields.The detailed mechanism has been studied and established theintermediacy of six-membered iridacycle intermediates.This methodology is applicable for awide range of carbocycles and heterocycles.The reaction endures a variety of functional groups.