Palladium(II)-catalyzed regiospecific and stereospecific cycloaddition reactions of aziridines and azetidines with heterocumulenes.
|Title:||Palladium(II)-catalyzed regiospecific and stereospecific cycloaddition reactions of aziridines and azetidines with heterocumulenes.|
|Abstract:||A study has been made of cycloaddition reactions of 3- and 4-membered ring nitrogen-containing heterocycles with heterocumulenes in the presence of Pd(II) catalyst. Bis(benzonitrile)palladium dichloride, Pd(PhCN)$\sb2$Cl$\sb2$, smoothly catalyzes the completely regioselective reactions of 1,2-disubstituted aziridines with N,N-diarylcarbodiimides to give imidazolidinimines in high yield. Similar cycloaddition reactions involving 1,2,3-trisubstituted aziridines and heterocumulenes (carbodiimides, isocyanates and isothiocyanates) provide regio- and stereospecific routes to imidazolinimines, imidazolidinones, and thiazolidinimines. Pd(PhCN)$\sb2$Cl$\sb2$-catalyzed cycloaddition reactions of chiral, optically active 1,2-disubstituted aziridines with heterocumulenes proceed with retention of configuration affording the corresponding five-membered ring heterocycles in high yield and in optically pure form. The study of the reaction of aziridines with N,N-diarylsulfurdiimide in the presence of a Pd(II) catalyst resulted in the discovery of a new and unusual cyclization furnishing imidazolidinethiones. Cycloaddition reactions of azetidines with heterocumulenes (carbodiimides and isothiocyanates) are also catalyzed by Pd(PhCN)$\sb2$Cl$\sb2$ and afford tetrahydropyridin-2-imines and tetrahydro-1,3-thiazine-2-imines, respectively, in a regio- and stereospecific manner in excellent yield. On the basis of results obtained, including spectroscopic studies and X-ray analysis, a mechanism has been proposed for the cycloaddition reactions of the N-heterocycles with heterocumulenes. A bis(azetidine)palladium complex was isolated and shown to be catalytically active for the reaction of azetidines with heterocumulenes. Numerous heterocyclic compounds have been prepared for the first time, some of them having the potential for pharmacological activity.|
|Collection||Thèses, 1910 - 2010 // Theses, 1910 - 2010|