C-Amino-1,2,4-triazoles are challenging polynitrogen substrates for metal-catalyzed arylation due to their multidentate character,enhanced coordinating ability and decreased nucleophilicity of the amino group.In the p...C-Amino-1,2,4-triazoles are challenging polynitrogen substrates for metal-catalyzed arylation due to their multidentate character,enhanced coordinating ability and decreased nucleophilicity of the amino group.In the present study,the Buchwald-Hartwig cross-coupling of diverse 3(5)-amino-1,2,4-triazoles with aryl chlorides and bromides delivering(hetero)arylamino-1,2,4-triazoles in good-to-excellent yields under Pd/NHC catalysis was developed.The use of Pd complexes with bulky NHC ligands such as IPr^(*OMe) and TPEDO(1,1,2,2-tetraphenylethane-1,2-diol)as an in situ Pd(Ⅱ)to Pd(0)reductant enabled the selective arylation of the NH_(2) group even in acidic NH unprotected substrates and deactivated 1-substituted 5-amino-and 4-substituted 3-amino-1,2,4-triazoles.The reaction mechanism and structure-activity relationships were studied with DFT calculations.A significant effect of the position of the N-substituent in the 1,2,4-triazole ring on the favorable reaction pathways was revealed.展开更多
Complexes of Pd(Ⅱ)with NHC ligands can suffer facile decomposition in the presence of alkali metal hydroxides,alkoxydes and other strong oxygen-containing bases via the reductive elimination of the NHC and Pd-coordin...Complexes of Pd(Ⅱ)with NHC ligands can suffer facile decomposition in the presence of alkali metal hydroxides,alkoxydes and other strong oxygen-containing bases via the reductive elimination of the NHC and Pd-coordinated base anion,the so-called O-NHC coupling.O-NHC coupling can represent a serious problem for the stability of Pd/NHC catalytic systems in numerous practically important reactions conducted in the presence of bases.In the present study,a new approach to stabilizing the Pd-NHC bond against cleavage by strong bases was developed.展开更多
基金supported by the Russian Science Foundation(RSF grant 22-23-00380).
文摘C-Amino-1,2,4-triazoles are challenging polynitrogen substrates for metal-catalyzed arylation due to their multidentate character,enhanced coordinating ability and decreased nucleophilicity of the amino group.In the present study,the Buchwald-Hartwig cross-coupling of diverse 3(5)-amino-1,2,4-triazoles with aryl chlorides and bromides delivering(hetero)arylamino-1,2,4-triazoles in good-to-excellent yields under Pd/NHC catalysis was developed.The use of Pd complexes with bulky NHC ligands such as IPr^(*OMe) and TPEDO(1,1,2,2-tetraphenylethane-1,2-diol)as an in situ Pd(Ⅱ)to Pd(0)reductant enabled the selective arylation of the NH_(2) group even in acidic NH unprotected substrates and deactivated 1-substituted 5-amino-and 4-substituted 3-amino-1,2,4-triazoles.The reaction mechanism and structure-activity relationships were studied with DFT calculations.A significant effect of the position of the N-substituent in the 1,2,4-triazole ring on the favorable reaction pathways was revealed.
基金supported by the Russian Science Foundation,RSF grant 19-73-10100(studies of Pd/NHC complex stability and catalytic activity)by the Ministry of Science and Higher Education of the Russian Federation,project 2019-0990(synthesis of Pd/NHC complexes).
文摘Complexes of Pd(Ⅱ)with NHC ligands can suffer facile decomposition in the presence of alkali metal hydroxides,alkoxydes and other strong oxygen-containing bases via the reductive elimination of the NHC and Pd-coordinated base anion,the so-called O-NHC coupling.O-NHC coupling can represent a serious problem for the stability of Pd/NHC catalytic systems in numerous practically important reactions conducted in the presence of bases.In the present study,a new approach to stabilizing the Pd-NHC bond against cleavage by strong bases was developed.
