Ring-Transformationen bei der Umsetzung von 3-(Dimethylamino)-2,2-dimethyl-2H-azirin mit 1-substituierten Imidazolidin-2,4,5-trionen |
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Authors: | Marlise Schl pfer-D hler,Heinz Heimgartner |
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Affiliation: | Marlise Schläpfer-Dähler,Heinz Heimgartner |
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Abstract: | Ring-Transformations in the Reaction of 3-(Dimethylamino)-2,2-dimethyl-2H-azirines with 1-Substituted Imidazolidine-2,4,5-triones Reaction of 1-substituted imidazolidine-2,4,5-triones ( = N-substituted parabanic acids; 2 ) and 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1 ) in i-PrOH or MeCN at room temperature yields 5,6,7,7a-tetrahydro-3H-imidazo[3,4-a]imidazole-5,7-diones 3 (Scheme 1). By 15N-NMR studies, using (3-15N)- 2a , it has been shown that only N( 1 ) in (15N)- 3a is labelled and, hence, N(4) stems from 1 , e.g. the azirine reacts via cleavage of the N(1)=C(3) bond. In MeCN at room temperature, the azacyclols 3 rearrange slowly to give monocyclic 2H, 5H-imidazol-2-ones 4 (Scheme 3); the 15N-label in (15N)- 4a is in position 1. Both reactions proceed via deep-seated skeletal rearrangements, most probably via ring-expansion/ring-contraction processes. |
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