Synthesis of (Z)-N-(2-amino-1, 2-dicyanovinyl)formamide O-alkyloximes and a study of their cyclization in the presence of base

摘要

The title compounds (3) have been prepared in high yield by reaction of (Z)-N-(2-amino-1, 2-dicyanovinyl)-formimidate with an alkoxyamine NH_2OR (R = CH_2Ph, Me). These compounds cyclize to the corresponding 5-amino-4-cyanoimidazoles 4 by reaction with ethanolic NaOH solution. In ethyl acetate and using DBU as a base, amidoximes 3 follow an unexpected cyclization pathway leading to a pyrimidine structure 5. Single-crystal X-ray structures have been obtained for both the amidoxime 3a and the pyrimidine 5a (R = CH_2Ph). A strong intramolecular H-bond in the amidoxime structure, which was identified both in the solid state and in solution, may be responsible for the unusual cyclization pattern observed in these compounds.