Multiple-Functionalizations Of Alkynes:Facile Synthesis Of Nitrogen-Containing Heterocycles

Nitrogen-containing heterocycles,as an important basic structure,are widely found in natural products and bioactive molecule and have been of great concern by many chemists.Among them,three-membered ring,azirines,and five-membered ring,isoxazolines,have proved to be an important skeleton in pharmaceutical and natural products as well as versatile precursors of multiclass compound.Therefore,the discovery of new simple and effective methods for constructing such compounds is a hot topic and remains an urgent challenge in organic synthesis.Unsaturated hydrocarbons are important staple product of petroleum and petrochemical industries.The transformation of unsaturated hydrocarbons is of great importance due to promote the development of organic synthesis and its core position in scientific development.In the past few decades,transformations of unsaturated hydrocarbons have attracted the increased interest of many chemists,in which many major breakthroughs such as the Sonogashira coupling reaction and Heck-type reactions,have been achieved.In recent years,functionzalization of unsaturated hydrocarbon using the free radicals strategy has aroused widespread interest and attention of chemical researchers because such radical strategy has the advantages of environment-friendly,high step economy and atomic economy.Therefore,efficient construction of nitrogen heterocyclic compounds by using unsaturated hydrocarbon as a substrate would be challenging with importantly academic and practical values.This dissertation mainly studies and describes the synthesis of nitrogen-containing heterocycles in recent years and conducts related research work around the construction of nitrogen heterocyclic compounds by utilizing alkynes through radical tandem technology.(1)Multiple-functionalizations of terminal alkynes construct of 2H-azirinesA new annulation reaction of terminal alkynes with sodium sulfinates using tert-butyl nitrite as a nitrogen source for the synthesis of functionalized 2H-azirines is described.This method is distinguished by its success achieved through the use of common,mostly commercially available starting materials under mild,catalyst-free conditions,as well as by its exquisite chemo-and site-selectivity,thus allowing the formation of 2,2-disulfonyl-2H-azirines via multiple-functionalizations of terminal alkynes.(2)Multiple-functionalizations of interminal alkynes afford of isoxazolinesA three-component reaction of interminal alkynes with sodium sulfinates using tert-butyl nitrite as a NO source for the synthesis of functionalized 4,5-dihydro-isoxazole was realized.This technology allows the complete functionalization of C(sp~3)-H bond and construction of three new chemical bonds in a single step,without the need of additional catalysts and metal reagents.This method provides an efficient access to isoxazoles.