Carbonicaciddiesters have been investigated as carbonylating agents in the direct reaction with pyrrole (HetNH). In the presence of superbases (DBU, P1-t-Bu, BTPP) as catalysts, the heteroaromatic substrate can be N-carbonylated by direct reaction with carbonicaciddiesters under not-severe experimental conditions. The carbonylation reaction makes accessible pyrrole N-carbonyl derivatives (HetNC(O)OR
N-Heteroaromatics HetNH, such as pyrrole (1), indole (2) and carbazole (3), have been selectively N-carbonylated by a direct reaction with diphenyl carbonate (DPC), used as an environmental friendly carbonyl active species in place of toxic and hazardous phosgene. The carbonylation reaction can be effectively catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), which can act as a base catalyst by
A new simple approach to the synthesis of unsymmetrical ureas HetNC(O)NRR′ (HetNH = pyrrole, indole, carbazole; R, R′ = H, alkyl, aryl) has been explored, which involves the direct reaction of the N-phenoxycarbonyl derivatives of pyrrole, indole and carbazole, HetNCO2Ph, with amines. The aminolysis reaction can be catalyzed by the amidine base DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) under usually
Carbonic Acid Diester Activation by Polymer-Bound DBU and Its Relevance to Catalytic N-Carbonylation of N-Heteroaromatics: Direct Evidence for an Elusive N-Carboxy-Substituted Amidinium Cation Intermediate
作者:Eugenio Quaranta、Antonella Angelini、Marianna Carafa、Angela Dibenedetto、Valentina Mele
DOI:10.1021/cs400661q
日期:2014.1.3
polymeric matrix, and provided the first direct evidence (FTIR and solid-state 13C NMR) of formation of a 8-carboxy-substituted 1,8-diazabicyclo[5.4.0]undec-7-enium cation in DBU-promotednucleophilicactivation of carbonicaciddiesters.