The thermal isomerization of deca-3, 7-diyne yields 1, 2-diethyl-3, 4-bismethylene-cyclobut- 1-ene. This forms by addition of two molecules of hydrogen chloride at− 78° several—with respect to the positions of the four alkyl substituents—isomeric 3, 4-dichloro-dimethyl-diethyl- cyclobut-1-enes. The mixture of isomers reacts with diironenneacarbonyl to give 1, 2- dimethyl-3, 4-diethyl-cyclobutadiene-irontricarbonyl in 14% yield. Trimethyl-ethyl- ...
