Citronellal → 1-(4,8-Dimethylnona-1,7-dien-1-yl)-4-(propan-2-yl)benzene

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To a stirred solution of sodium (21 g, 0.9 at) in 1500 ml of absolute ethanol was added 388 g of p-isopropylbenzyltriphenylphosphonium chloride. The resulting phosphorane solution was cooled to 15°-20° C. (The light orange color fades when the temperature is lowered-) Freshly vacuum distilled citronellal (150 g, 1 mol.) was added dropwise while keeping the reaction mixture at reflux for 4 hours. The cooled reaction mixture was filtered to remove sodium chloride, most of the alcohol was distilled off in vacuo and 500 ml of hexane was added. The triphenylphosphineoxide was allowed to crystallize and filtered off. The solvents were removed from the mother liquors under vacuum and another 500 ml of hexane added. Cooling afforded another crop of triphenylphosphineoxide. The hexane was again evaporated and the residue distilled yielding, after a small forerun of isopulegol (a contaminant of citronellal), 200 g (82%) of the desired product. bp. 150°-145° C/0.1 mm. Ratio of E to Z is app. 40:60. nD25 =1.5172.

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