Stabilization of (N-methyleneamino)imidoylketenes: synthesis of dipyrazolo[1,2-a;1′,2′-d][1,2,4,5]tetrazines |
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Authors: | Natalia A Lisowskaya Andrei N Maslivets |
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Institution: | a Department of Organic Chemistry, Perm State University, 15 Bukireva Str., 614990 Perm, Russian Federation b Institute of Problems of Chemical Physics, Russian Academy of Science, 14 Institutskii Prosp, 142432 Chernogolovka, Moscow Region, Russian Federation |
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Abstract: | Thermolysis of substituted methyl 1-methyleneamino-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates 2a,b led to substituted dimethyl 3,9-dioxo-1,5,7,11-tetrahydro-1H,7H-dipyrazolo1,2-a;1′,2′-d]1,2,4,5]tetrazine-1,7-dicarboxylates 4a,b and methyl 2,5-dihydro-5-oxo-1H-pyrazole-3-carboxylates 5a,b as minor products. The structure of compound 4a was determined by X-ray crystallography. The proposed mechanism of this conversion includes generation of (N-methyleneamino)imidoylketenes 6a,b and its intramolecular transformation to azomethine imines—5-oxo-2,5-dihydropyrazole-1-methylium-2-ides 7a,b, which undergo dimerization in head-to-tail manner yielding products 4a,b and partially hydrolyse to compounds 5a,b. |
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Keywords: | Pyrrole-2 3(1H)-diones (N-Methyleneamino)imidoylketenes Azomethine imines Dipyrazolo[1 2-a 1&prime 2&prime -d][1 2 4 5]tetrazines |
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