[4+2] Cycloaddition of Dimethyl 1,2,4,5-Tetrazine-3,6-dicarboxylate with EWG-Substituted Primary Ketene <i>N</i>,<i>O</i>-Acetals : Synthesis of Tetrafunctional Pyridazines and Pyrroles
作者:Reinhard Troschütz、Jörg Müller
DOI:10.1055/s-2006-926425
日期:2006.5
A series of EWG-substituted primary ketene N,O-acetals were reacted with tetrazine-3,6-dicarboxylate yielding, by [4+2] cycloaddition, tetrafunctionalized pyridazines, which possess an EWG group, a primary amino function and two ester moieties. Reductive ring contraction of pyridazines gave aminopyrrole derivatives. Treatment of cyanamide with tetrazine-3,6-dicarboxylate led to a 5-amino-1,2,4-triazine derivative, which was rearranged to 4-aminoimidazole-2,5-dicarboxylic acid dimethyl ester.
一系列由 EWG 取代的原酮 N,O-乙醛与四嗪-3,6-二羧酸反应,通过 [4+2] 环加成反应生成了四官能化的哒嗪,这些哒嗪具有一个 EWG 基团、一个原氨基官能团和两个酯分子。对哒嗪进行还原缩环,可得到氨基吡咯衍生物。用四嗪-3,6-二羧酸处理氰酰胺可得到 5-氨基-1,2,4-三嗪衍生物,该衍生物被重新排列为 4-氨基咪唑-2,5-二羧酸二甲酯。