Cyclooctadiene and Cyclododecatriene from Butadiene

5-Cyclooctadiene (COD) is an intermediate for the manufacture of poly-octenamers, while 1,5,9-cyclododecatriene (CDT) is the starting material for the manufacture of dodecanoic acid and lauryl lactam. The latter is converted to the polyamide fiber Vestamide (DuPont). Both COD and CDT are made from butadiene (Equations 21 and 22). 

Metallacycles, such as those obtained from butadiene and nickel(O), represent an important class of compounds containing two metal-carbon a-bonds and are useful in transition metal-controlled organic syntheses. 

Metallacycles have also been prepared from two molecules of alkenes or alkynes or from palladated o-alkyl- or aryl- substituted aryls by C-H activation. Metallacycles usually have five- or six-membered ring structures, and four-membered metallacycles have been shown to be intermediates in metathesis (Chapter 6). 

The reactivities of metallacycles obtained from the same substrate with different metals can vary dramatically for example, in contrast to nickel, the palladacyles obtained from butadiene mainly convert into open-chain dimers as a consequence of the greater tendency of palladium to undergo p-hydrogen elimination. 

Interestingly a Ziegler Natta catalyst (Chapter 7) consisting of TiCU associated with an aluminium alkyl co-catalyst in a 1 1 molar ratio, polymerizes butadiene, but it is also able to afford cyclododecatriene provided that the TiCU/co-catalyst molar ratio is kept approximately to 0.1 instead of 1 [M. Rapoport and D. L. Sullivan, Can. Patent 1 055 052 (1979), to DuPont]. Although the mechanism is unclear, this is a good example of how delicate can be the modulation of a catalytic system for a selective synthesis. 

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