Acyclic -6,8-nonadien

A variety of cycloheptenols 24 can be synthesized in enantiomerically pure form with high chemical yields by ring-closing metathesis of acyclic, chiral polyoxyge-nated 1,8-nonadiene precursors 23 derived from carbohydrates [Eq. (6.20)]. ... 

Yang and Burton studied reductive radical additions of iododifluoroacetate 37 to olefins 38 and dienes catalyzed by 6-17 mol% of a catalyst generated from NiCl2 and stoichiometric amounts of zinc in the presence of water (Fig. 8) [90, 91]. Olefins gave the reductive addition products 40a in 60-83% yield, while 1,5-hexadiene or 1,8-nonadiene provided double addition products exclusively in 55% and 73% yield. 1,7-Hexadiene gave an inseparable mixture of the expected acyclic double addition product and a tandem addition/cyclization product, in which the former dominated. The radical nature of the addition is supported by inhibition of the reaction by para-dinitrobenzene. The reaction proceeds probably via initially formed atom transfer product 39, which is subsequently reduced by nickel(0) and zinc. This is supported by deuterium incorporation, when D20 was used instead of water. No deuterium incorporation was observed with THF-dg, thus ruling out hydrogen transfer from the solvent. 

Acyclic and cyclic allenes are converted to alkenes at 60 °C under atmospheric pressure of hydrogen with [RhCl(PPh3)3]. 1,2-Nonadiene (26), 3-ethyl-1,2-pentadiene and 1,2-cyclotridecadiene are hydrogenated to give cts-2-nonene (27), 3-ethyl-2-pentene and cyclotridecene (cis trans = 85 15), respective-... 

A second method of using olefin metathesis to prepare polymers is by acyclic diene metathesis, or ADMET. As the name suggests, ADMET involves olefin metathesis of an open-chain substrate with two double bonds at the ends of a long chain, such as 1,8-nonadiene. As the reaction proceeds, the gaseous ethylene by-product escapes, thereby driving the equilibrium toward polymer product. So efficient is the reaction that polymers with molecular weights as high as 80,000 amu have been prepared. 

---