The unique linear linkage of isobutene to generate highly valuable C8 precursors for plasticizers is feasible by using special nickel catalysts. (4-Cyclooctene-1-yl)(1,1,1,5,5,5-hexafluoro-2,4-acetylacetonato)nickel and aluminum-alkyl-activated nickel acetylacetonates produce isobutene dimers with high selectivities of up to 95%. Moreover, selectivity for the head-to-head products (2,5-dimethylhexenes) is remarkably high at up to 99%. Additionally, novel C12 isobutene trimers are also formed with a very high selectivity of up to 99% for the linear linkage. The trimer structure (2,5,8-trimethylnonenes) reflects the stepwise characteristic of the reaction mechanism. Pathways of insertion and activation and the deactivation processes of the catalyst are discussed in detail.
An efficientp rotocolw as developed to prepare as erieso fd ialkylpiperazines via Rh-catalyzed bis-hydroaminomethylation of linear aliphatic alkenes with piperazine.T he well-known Rh/Biphephos catalytic system was applied, yielding the desired dialkylpiperazines within six tandemc atalytic steps,a lready at low catalyst loadings of 0.1mol%. Fort he model alkene 1-octene,g ood yields and linearities of 80% and 77:23, respectively,w ere achieved under optimized conditions.I nfluences on the catalytic system regarding n/iso ratio, possible side reactions and the reactionp ath are discussed on the basis of yield vs. time plots and parameter optimization. With the developedg eneral protocol, other linear, functionalized and branched substrates were effectively transformed to the corresponding linear N,Ndisubstituted piperazines.
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