Stereoselective Nucleophilic Addition Reaction Of Alkynes Catalyzed By Cyclic Trimeric Phosphazene Base

Enamines have played an important role in many fields because of their special medicinal properties.They are key structural units of natural products and drugs and important intermediates of chiral amines.Vinyl sulfides play a prominent role in synthetic organic chemistry as well.They are extensively used as synthetic equivalents of enolateions and acyl anions.In addition,vinyl sulfides are valuable intermediates in the synthesis of oxetanes,spirocyclic systems and other organic compounds.Vinyl sulfides also present interest as candidate pesticides and bactericides.Therefore,the development of an efficient and versatile method capable of synthesizing enamines and vinyl sulfides is of great importance in organic synthesis.Catalytic addition reaction using organic base catalysts is one of the important advances in organic synthesis.As a kind of metal-free organic base,cyclic trimeric phosphazene base（CTPB）has been favored due to its strong basicity,and has been widely used in polymerization.However,it has not been used in the synthesis of small organic molecules.This paper developed a simple and efficient Anti-Markovnikov stereoselective hydroamination and hydrothiolation of aromatic and heteroaromatic alkynes using a metal-free cyclic trimeric phosphazene base.With a ratio of alkynes/nucleophilic=1.5,CTPB（10 mol%）as catalyst,DMSO（1 mL,c=0.5 M）as solvent,the reaction was conducted at 120oC for 24 hours.Enamine and vinyl sulfur compounds with different structures were synthesized with good to excellent yield and good selectivity.A broad substrate scope of alkynes and nucleophiles was demonstrated,including aryl and heteroaryl alkynes,terminal and internal alkynes,different N-heterocycles,thiols and thiophenols.This versatile and cost-efficient approach with good stereoselectivity and excellent functional group tolerance provided new opportunity for the organocatalyzed hydrofunctionalization of alkynes.The structures of all synthesized new compounds have been characterized by ¹H NMR,¹³C NMR,and HRMS.Their configuration was determined by ¹H NMR.