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Paper | Special issue | Vol 40, No. 2, 1995, pp.681-689
Published online, 1st January, 1970
DOI: 10.3987/COM-94-S56
Crosss-conjugated and Pseudo-Cross-conjugated Mesomeric Betaines, 19. Cycloaddition Products from Mesomeric Pyrimidiniumolates and TCNE and Their Thermal Ring Transformation Reaction

Thomas Kappe, Wolfgang Lube, Kurt Thonhofer, Christoph Kratky, and Ulrike G. Wagner

*Institute of Organic Chemistry, Karl-Franzens-University Graz, Heinrichstr. 28, A-8010 Graz, Austria


The bicyclic pyrido-pyrimidine mesoion (2) reacts with TCNE under the loss of HCN to yield the tricyanovinylated derivative (3). However, monocyclic pyrimidine betaines (4a-d) (substituted at C-5) afford with TCNE 14-dipolar cycloaddition products (5a-d). Compounds (5c,d) (with CH2 groups at the malonyl moiety) rearrange above 200°C under the loss of HCN and phenyl isocyanate to yield cyclopenta[d]pyrmidines (6a,b).