3,7-Dimethylocta-2,6-Dienal → 4,8-Dimethylnona-3,7-dien-2-ol

Participants

Reaction Steps

A mixture of 671.2 g of citral and 185.6 g of diethyl ether is added to an addition funnel. The citral mixture is then added dropwise over a five hour period to a nitrogen blanketed, stirred, 5 L, 3-neck, round bottom flask equipped with a reflux condenser containing 1.6 L of 3.0 M methylmagnesium bromide solution and an additional 740 ml of diethyl ether. The reaction flask is situated in an ice water bath to control exotherm and subsequent ether reflux. After addition is complete, the ice water bath is removed and the reaction allowed to mix for an additional 2 hours at 20-25° C. at which point the reaction mixture is added to 3.5 Kg of cracked ice with good mixing. To this mixture is added 1570 g of 30% sulfuric acid solution. The aqueous acid layer is drained and the remaining ether layer washed twice with 2 L of water. The ether layer is concentrated by evaporation of the ether under vacuum to yield 720.6 g of 4,8-dimethyl-3,7-nonadien-2-ol. To a glass autoclave liner is added 249.8 g of the 4,8-dimethyl-3,7-nonadien-2-ol, 5.8 g of 5% palladium on activated carbon and 200 ml of n-hexane. The glass liner is sealed inside a 3 L, stainless steel, rocking autoclave and the autoclave purged twice with 250 psig N2, once with 250 psig H2 and then charged with 100 psig H2. Upon mixing, the reaction initiates and begins consuming H2 and exotherms to 75° C. The autoclave is heated to 80° C., boosted to 500 psig with H2, mixed for 3 hours and then cooled to 30° C. The reaction mixture is removed from autoclave, filtered to remove catalyst and concentrated by evaporation of n-hexane under vacuum to yield 242 g of 4,8-dimethyl-2-nonanol.

Provenance & Evidence