A New Synthesis of 1,2-Diazetines via Simple Cycloacylation Reactions

Abstract

Several new 1,2-diazetines (4a-e) were synthesized via simple cycloacylation reactions of various monoalkylhydrazines (5a-c) with bis-imidoyl chlorides of oxalic acid ( 1).An X-Ray crystal structure analysis obtained from single crystals of 4a reveals an additional double bond in the 4-membered ring system.Treatment of these heterocycles with strong bases formed delocalized anions (6) which can be methylated giving 1,2-disubstituted diazetidines (7a,b).Alternatively, the latter derivatives can be synthesized via a cycloacylation employing 1,2-dimethylhydrazine and bis-electrophiles (1).Four-membered nitrogen heterocycles are wide spread in synthetic organic chemistry and in nature in the form of biological active compounds such as ß-lactams.However, four-ring heterocycles that bear two nitrogen atoms in 1,2-position are quite rare and only a few examples have been reported in the literature. 1 To our knowledge, there are few derivatives which possess an additional double bond between nitrogen and carbon ring atoms. 2 In this article, we describe a new and efficient synthesis of 1-substituted 4-imino-1,2-diazetines (4a-e) and discuss their alkylation which leads to the 1,2disubstituted diazetidine-3,4-diimines (7a,b).Our aim was originally to synthesize triazines (3) by cyclization of amidrazones (2) 3 with bis-imidoyl chlorides of oxalic acid (1).Derivatives (3) should preferably exist in the prototropic form (3') as compared to corresponding five-membered heterocycles. 4This cyclic arrangement of the amidine substructure should be able to efficiently complex various metal ions. 5