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Ringerweiterungen und Ringverengungen bei der Umsetzung von 1, 3‐Oxazolidin‐2, 4‐dionen und 1, 3‐Thiazoiidin‐2, 4‐dion mit 3‐Amino‐2 H ‐azirinen
Author(s) -
Ametamey Simon M.,
Heimgartner Heinz
Publication year - 1990
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19900730520
Subject(s) - chemistry , zwitterion , stereochemistry , thiazolidine , oxazolidine , ring (chemistry) , bicyclic molecule , medicinal chemistry , molecule , organic chemistry
Ring Enlargements and Ring Contractions in the Reaction of 1, 3‐Oxazolidine‐2, 4‐diones and l, 3‐Thiazolidine‐2, 4‐dione with 3‐Amino‐2 H ‐azirines The reaction of 3‐amino‐2 H ‐azirines 1 and 1, 3‐oxazolidine‐2, 4‐diones 2 in MeCN at room temperature leads to 3, 4‐dihydro‐3‐(2‐hydroxyacetyl)‐2H‐imidazol‐2‐ones 3 in good yield ( Scheme 2 , Table 1 ). A reaction mechanism proceeding via ring enlargement of the bicyclic zwitterion A to give B, followed by transannular ring contraction to C, is proposed for the formation of 3 . This mechanism is in accordance with the result of the reaction of 2a and the 15 N‐labelled 1a *: in the isolated product 3a *, only N(3) is labelled ( Scheme 1 ). The analogous reaction of 1 and 1, 3‐thiazolidine‐2, 4‐dione ( 5 ) is more complex ( Schemes 4 and 5 , Table 2 ). Besides the expected 3, 4‐dihydro‐3‐(2‐mercaptoacetyl)‐2 H ‐imidazol‐2‐ones 7, 5‐amino‐3, 4‐dihydro‐2 H ‐imidazol‐2‐ones of type 8 and/or N‐(1, 4‐thiazin‐2‐ylidene)ureas 9 are formed. In the case of 2‐(dimethylamino)‐1‐azaspiro[2. 3]hex‐1‐ene ( 1d ), the postulated eight‐membered intermediate 6d could be isolated. Its structure as well as that of 9f has been determined by X‐ray structure analysis. A reaction mechanism for the formation of the 1, 4‐thiazine derivatives of type 9 is proposed in Scheme 6 .