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1-(Trifluoromethyl)-3,4-dihydropyrrolo-[1,2-a] pyrazines: synthesis and reactions with O- and N-nucleophiles

“…One of the simplest and most convenient methods of preparing pyrrolo[1,2-a]pyrazines is based on the condensation of 2-acylfurans with ethylene diamine [6]. However, this synthetic method is only used for preparing 1,6-alkyl-and aryl-substituted pyrrolo[1,2-a]pyrazines, the difficultly obtainable pyrrolo[1,2-a]pyrazines with a functional group in position 1 not previously being available by this procedure.…”

Unexpected tandem condensation of 2-furonitriles with diethylenetriamine

“…The method widely used for synthesis of 1,6-dialkyl-substituted pyrrolo[1,2-a]pyrazines is based on the reaction of substituted 2-acylfurans with ethylenediamine [3].We proposed that exchange of the starting 2-acylfurans and ethylenediamine for the corresponding 2-furonitriles and diethylenetriamine respectively permit the preparation of more complex structures. Reaction of 2-furonitriles with ethylenediamine, however, gave only the 2-(2-furyl)-4,5-dihydro-1H-imidazoles 2a,b.…”

“…The method widely used for synthesis of 1,6-dialkyl-substituted pyrrolo[1,2-a]pyrazines is based on the reaction of substituted 2-acylfurans with ethylenediamine [3].…”

Azacycloalkanes. XXXVII: 3,4-Dihydro-5H-pyrrolo[1,2-a]-diazepine and Its Conversions

“…In particular, octahydropyrrolo[1,2-a]pyrazine fragment enters into the structure of the effective antianginal drug nonachlasine [3]. Previously, we have developed a new method for the synthesis of this fragment using the reduction of 3,4-dihydro[1,2-a]pyrazine, which can be obtained via the reaction between 2,5-dimethoxy-2-dimethoxymethyltetrahydrofuran (I) with ethylenediamine in acetic acid [4,5]. The present paper reports on the synthesis and transformations of a cyclohomologous compound, pyrrolo[1,2-a]diazepine (II), obtained using Scheme 1.…”

“…This result indicates that the reaction proceeds predominantly via the formation of an intermediate N-(3-aminopropyl)-2-(dimethoxymethyl)pyrrole (III). Previously, it was found [4] that an analogous reaction of acetal I with ethylenediamine yields a homologous product, 1,2-bis-[N-(2¢-formylpyrryl]ethane, with a yield of 37%. This result shows that the rate of pyrazine ring closure is about twice as large as that for the diazepine cycle.…”