Stable five-membered-ring allenes with second-row elements only: not allenes, but zwitterions.
A pyrazole derivative, considered as the stable five-membered cyclic allene 1 a by Dyker, Bertrand, et al., is reinterpreted to be a zwitterion 1 b. It is shown that the bonding characteristics typical for an allene are not possible for structure 1 a. Ar = 2,6-dimethylphenyl.
Christl
Manfred
M
Engels
Bernd
B