1,3-Butadiene → cis,cis-1,5-Cyclooctadiene

온도

120 °C

A Predried six ounce aerosol compatibility bottle equipped with a magnetic stirring bar was charged in a dry box with 0.17 g (0.20 mmol) of Ni2 (μ-PPh2)2 (PEt3)3, 10 ml of benzene and then capped. The capped bottle was removed from the dry box and 20.65 g (0.382 mol) of 1,3-butadiene was added. The bottle was heated in an oil bath as the contents were magnetically stirred. The temperature was gradually increased. After about 1 hour at a temperature opf about 80° C the pressure in the bottle was 93 psig. The absence of any observed pressure drop was taken to indicate that no significant reaction had yet occurred. After heating for about 30 more minutes the temperature was about 118° C and the pressure in the bottle about 160 psig. After one hour at this temperature, the pressure had fallen to 143 psig. The reaction mixture was then cooled. After being allowed to set at room temperature over the weekend the reaction mixture was heated to about 120° C. After about an hour at this temperature the pressure in the bottle had dropped from 110 psig to 20 psig. The reaction mixture was then cooled and an additional 19.23 g (0.356 mol) of 1,3-butadiene was added. The reaction mixture was then reheated to 120° C. After about 2 more hours at 120° C, the pressure again decreased to about 20 psig. The reaction mixture was then again cooled and a further 29.67 g (0.549 mol) of 1,3-butadiene was added. After heating this mixture for about 2 more hours at 120° C the pressure dropped to about 38 psig. The reaction was then terminated although the solution still retained its homogeneous dark green appearance. The mixture was then exposed to air to destroy the catalyst and filtered. The filtrate was distilled to afford 28.7 g of 1,5-cyclooctadiene, 5,7 g of 1,5,9-cyclododecatriene, and other products.