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Synthesis 2006(3): 514-518  
DOI: 10.1055/s-2006-926272
PAPER
© Georg Thieme Verlag Stuttgart · New York

Δ2-1,2-Diazetines: Regioselective Acylation Reactions and Rearrangement into 4H-1,3,4-Oxadiazines

J. Fleischhauera, R. Beckert*a, J. Westona, M. Schmidta, H.-J. Flammersheimb, H. Görlsc
a Institute of Organic and Macromolecular Chemistry, Friedrich Schiller University, Humboldtstraße 10, 07743 Jena, Germany
b Institute of Physical Chemistry, Friedrich Schiller University, Lessingstraße 8, 07743 Jena, Germany
c Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University, Lessingstraße 8, 07743 Jena, Germany
Fax: +49(3641)6948212; e-Mail: Rainer.Beckert@uni-jena.de;
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Publication History

Received 18 July 2005
Publication Date:
11 January 2006 (online)

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Abstract

Reaction of a 1-substituted Δ2-1,2-diazetine with acid chlorides or anhydrides resulted in the derivatives 3a,b,f that have been acylated at a ring position. On the other hand, trifluoroacetic anhydride yields a new 1,3,4-oxadiazine 4e under the same conditions. The structure of 4e could be confirmed by X-ray structural analysis. Acylated 1,2-diazetidines of type 3a,b can be nearly quantitatively transformed into 1,3,4-oxadiazines 4a,b by thermally induced ring-expansion reactions. Differential scanning calorimetry measurements provide evidence for a monomolecular mechanism in which a strong dependence of the acyl group on the rate of reaction is observed.

Key words

acylations - ring expansion - regioselectivity - heterocycles - imines