Dimerization of Butadiene and Isomerization of Its Dimers by Co Compound-Alkali Metal Catalyst

Oligomerization of butadiene was carried out in the presence of tetrahydrofuran at 40°C for 16 hr using Co compound-Alkali metal catalyst to produce a linear dimer 21 by 73°C/100 mmHg, in 51% yield. C2C absorbed 3 mol-equivalent H, to give 3-methylheptane but was not identical with 5-methylhepta-1, 3, 6-triene, C 1 obtained by the reaction catalyzed by Co compound-A1R3. IR and NMR spectra of C 2 J and maleic anhydride adduct of C 2 J showed that C2C was 3-methylhepta-1-trans-3-trans-5-triene. Other products were C 1, octa-1, 3, 6- triene, octa-2, 4, 6-triene and a trace of unknown dimer. By the fact that C 1 J and C 2 were produced equally at the first step of the dimerization reaction, but C 2 J finally became the main product and that C 1 J was isomerized to C 2 J by this catalyst, it was assumed that C 1 J was the initial product and then isomerized to C 2 under the reaction conditions. Octa-1, 3, 6-triene and 2, 6-dimethylocta-1, 3, 6-triene were also isomerized to octa-2, 4, 6- triene and 2, 6-dimethylocta-2, 4, 6-triene by this catalyst.