1,2-Nonadiene hydrogenation

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. 

An alternative procedure is available for the preparation of iodocarbonates which utilizes homoallylic carbamates as the starting material. For example, (/f )-( )-5-(aminocarbonyloxy)-l-benzyloxy-2,8-nonadiene [12, R1 = ( )-CH2OBn R2 = (CH2)2CH = CH2 R3 = H]9 with two equivalents of iodine in a two-phase medium consisting of diethyl ether and sodium hydrogen carbonate solution at 20 CC affords the corresponding cyclic iodocarbonate 13, a precursor of 1,3,5-triols1 °, in 76% yield and 93 7 (cis1,traits ) selectivity. 

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-... 

Recently, phospholipids, e.g., lecithin, were classified as nutraceutical foods (Colbert, 1998). The off-flavor associated with lecithin produced in fermented dairy products includes 2,4-nonadienal, 2,4-decadienal, and hydrogen peroxide (Suriyaphan etal., 2001). 

Warwel et al. [27] synthesized 1,8-nonadiene in 75 % yield via ethenolysis of cy-cloheptene over a Rc207/Al203 catalyst (at 60 °C and an ethene pressure of 80 bar). The diene was subsequently subjected to intermolecular metathesis (release of ethene), again over a rhenium oxide catalyst (at 35 °C and 15 torr vacuum), giving 80% yield of 1,8,15-hexadecatriene. The latter was converted, via oxidation, intramolecular aldol condensation, and hydrogenation, to muscone (3-methylcyclo-pentadecanone), an important perfume ingredient. 

Figure 8.3. The half-hydrogenated state of cycle-1,2-nonadiene shown in plan as (A) a JTs structure and (B) a jrcr structure.

Upon heating, spiro[4.4]nona-l,3-diene gives a number of bicyclo[4.3.0]nonadiene isomers which interconvert by 1,5-hydrogen shifts, but at higher temperatures, a 1,3-shift occurred to give bicydo[4.3.0]nona-1,6-diene which at still higher temperatures ultimately gave indane (Scheme 10.59). ... 

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