Nickel-Catalyzed Synthesis of Cyclic Compounds

Nickel catalysts for the syntheses of cyclic compounds were first successfully utilized by Reppe, who was able to prepare cyclooctatetraene from acetylene (65). This eight-membered ring synthesis, and also the preparation of cyclic products from strained olefins (e.g., bicycloheptene and norbornadiene) and acrylonitrile, have been adequately reviewed elsewhere (7) and will therefore not be considered further. A short account of the cyclization reactions of butadiene using nickel-containing catalysts has appeared previously in this series (/). The discovery of new synthetic possibilities and a deeper understanding of the mechanism of these reactions justify a more extensive treatment. 

As early as 1954, Reed (66) had shown that butadiene reacts in the presence of nickel-containing catalysts to produce cis,cis-1,5-cyclooctadiene. The catalyst employed was the so-called Reppe-type catalyst, (I,ig)2Ni (CO)2 (where Lig = phosphine or phosphite), which was previously 

Before entering into a detailed discussion of the nickel-catalyzed reactions of olefins, the convention we will use to describe the stereochemistry of the intermediate 77-allyl complexes should be mentioned. As an example, consider the bis(Tr-allyl) C8 chain postulated as an intermediate in the 

This is preferable, in this case, to the usual syn and anti terminology, since ring closure is accompanied by formation of double bonds having the same configuration as the 7r-allyl group. 

The reduction of nickel(II) in the presence of butadiene as the only available ligand (i.e., naked-nickel3) (69) produces a catalyst which is able to trimerize butadiene to a mixture of all-trans- trans,trans,cis- and trans,cis,cis-i, 5,9-cyclododecatriene in which the all-trans form predominates. 

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