The Pseudo‐Michael Reaction of 2‐Hydrazinylidene‐1‐Arylimidazolidines with Diethyl Ethoxymethylenemalonate |
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| Authors: | M Aletańska‐Kozak A A Kaczor T M Wróbel A E Kozio? K Suwińska I Dyba?a K Pihlaja D Matosiuk |
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| Institution: | 1. Department of Synthesis and Chemical Technology of Pharmaceutical Substances with Computer Modelling Lab, Faculty of Pharmacy with Division of Medical Analytics, Medical University of Lublin, Lublin, Poland;2. School of Pharmacy, University of Eastern Finland, Kuopio, Finland;3. Faculty of Chemistry, Maria Curie‐Sk?odowska University, Lublin, Poland;4. Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland;5. Department of Chemistry, University of Turku, Turku, Finland |
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| Abstract: | The pseudo‐Michael reaction of 2‐hydrazinylidene‐1‐arylimidazolidines with diethyl ethoxymethylenemalonate (DEEM) was investigated. The reaction yields the chain adduct, namely diethyl{2‐(1‐arylimidazolidin‐2‐ylidene)hydrazinyl]methylidene}propanedioates. This is contrary to the pseudo‐Michael reaction of DEEM with 1‐aryl‐4,5‐dihydro‐1H‐imidazol‐2‐amines that does not allow isolation of chain derivatives and leads to cyclic imidazo1,2‐a]pyrimidine derivatives while even at thermodynamic control. At first cyclization of diethyl{2‐(1‐arylimidazolidin‐2‐ylidene)hydrazinyl]methylidene}propanedioates leads to ethyl 1‐aryl‐5(1H,8H)oxo‐2,3‐dihydro‐imidazo2,1‐c]1,2,4]triazepine‐6‐carboxylates. 1,5‐Sigmatropic shift, following the cyclization, caused isomerization of 5(1H,8H)oxo‐2,3‐dihydro‐imidazo2,1‐c]1,2,4]triazepine‐6‐carboxylates to ethyl 1‐aryl‐5(1H)hydroxy‐2,3‐dihydroimidazo2,1‐c]1,2,4]triazepine‐6‐carboxylates. Presence of both isomers in the reaction product was detected in the NMR spectra. The structure of all the compounds was confirmed with spectroscopic studies (1H NMR and MS). The structure of diethyl{2‐(1‐phenylimidazolidin‐2‐ylidene)hydrazinyl]methylidene}propanedioate was also confirmed by X‐ray crystallography. In the addition reaction, thermodynamics and HOMO–LUMO orbitals of the reactants were studied by using quantum chemical calculations. |
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