V. Figala et al., ANOMETHYLENE-1-(1-PYRIDINIO)-3-CYCLOPENTENE-1-IDES - NOVEL PYRIDINIUMYLIDES OF THE CYLOPENTADIENE SERIES, Tetrahedron letters, 34(40), 1993, pp. 6375-6378
Pyridiniotetrabromocyclopentadienides react with tetracyanoethylene to
form the title ylides in which the pyridinium ring and the cyclopente
nide moiety are orthogonally arranged.