Synthesis and mechanism of formation of novel 2,5-dihydro-2,5-diimino-3,4-di[(N,N-dimethylamino)methylideneamino]pyrroles and 5-amino-3,4-di[(N,N-dimethylamino)methylideneamino]-2H-2-iminopyrroles

✍ Scribed by M. José Alves; M. Alice Carvalho; M. Fernanda; J. R. P. Proença; Brian L. Booth; Robin G. Pritchard

• Book ID: 102892891
• Publisher: Journal of Heterocyclic Chemistry
• Year: 1999
• Tongue: English
• Weight: 561 KB
• Volume: 36
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570360129

✦ Synopsis

Abstract

Formation of 5‐amino‐3,4‐di[(N,N‐dimethylarnino)methylidenearnino]‐2__H__‐2‐iminopyrroles 3 from the reaction of (Z)‐N^1^‐(2‐amino‐1,2‐dicyanovinyl)‐N^2^‐substituted‐formamidines 1 with dimethylformamide diethyl acetal has been shown to occur by initial formation of (Z)‐N^1^‐{l,2‐dicyano‐2‐[N,N‐dimethylamino)methylideneamino]vinyl}formamidines 8 (isolated), followed by base catalysed cyclisation and imi dazole ring opening by dimethyl amine. The kinetic product of the ring opening reaction is the 2,5‐diimino2,5‐dihydropyrrole derivatives 11, which have been isolated and characterized spectroscopically and by a single crystal X‐ray analysis on the R = Ph derivative. In solution at room temperature the N‐aryl derivatives undergo a rapid Dimroth rearrangement to give the thermodynamic ally more stable isomer 3, but compound 11 (R = Me) is much more stable in solution.