Metal-Catalyzed Synthesis Of Amides

Undoubtedly,amide bond is essential to sustain life.For Example,it is the most basic covalent bond in peptides(e.g.enzymes).Meanwhile,amide bond can be seen in a variety of natural products and modern pharmaceutical molecules of interest.So,numerous biologists and chemists have given their priority to the construction of amide bond.However,despite the abundance of the building methods,most of them involve the use of stoichiometric amount of coupling reagents,which increases the expense accordingly.Hence,this contradiction motivates us to continue the exploration of developing novel metal-catalyzed methods for achieving amide bonds.This paper mainly centers on the preparation of ?-benzenesulfonamido ketones and amides containing isoxazoline.The details are as follows:1.Isoxazolines have been reported to be of synthetic and pharmaceutical importance,and amides containing isoxazolines provide more posibility for medical research.With the synergistic effect of(Diacetoxyiodo)benzene(PIDA)and Zinc trifluoromethanesulfonate,the ? carbon-carbon bond of ?,?-unsaturated ketoximes cleavaged to give intermediate nitrile oxides.The counterpart so-obtained reacts with nitriles,and elaborated N-allylamides.This is followed by intermolecular 1,3-dipolar cyclization of nitrile oxides and N-allylamides,infrequently affording the amides containing isoxazoline.2.In view of the fact that N-centered radical is difficultly available and is reluctant to react with carbon-carbon triple bond,we envisioned that maybe N-Fluorobenzenesulfonimide(NFSI)can be utilized as precusor of N-centered radical and the latter then reacted with arylpropiolic acid to deliver benzenesulfonimide-functionalized alkynes.Happily,we obatined ?-benzenesulfonamido ketones.The poposed mechanism is as follows: NFSI is activated by cuprous salt,generating nitrogen-centered radical which regioselectively added to the triple bond of alkyne silver intermediate,distant from the aryl group.Subsequent 1,4-aryl migration motivates the loss of sulfur dioxide.Then,a oxidation/nucliphilic attack of water/semi-pinacol rearrangement sequence finally furnishes ?-benzenesulfonamido ketones.