Acetic Acid → 2-Oxo-2-ethoxy-3,3,5-trimethyl-5-diethylphosphono-1,2-oxaphospholane

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Reaction Steps

98 g of mesityl oxide (1.0 mole) and 415 g of diethyl phosphite (3.0 moles) were dissolved in 300 ml of benzene. 200 ml of this solution was heated to the boiling point. A catalytic amount of sodium was added whereupon a vigorous exothermic reaction commenced, and the mixture boiled by itself after removal of the heating bath. After the sodium dissolved, the reaction came practically to a stop and was initiated again by addition of a further amount of sodium. In this manner sodium was added until the main reaction was over. Then about one third of the remaining solution was added, and this was also reacted as previously by adding sodium. The remaining two thirds of the solution were then reacted in the same way. Altogether 3.0 g of sodium was used over the course of 25 minutes. The entire reaction mixture was allowed to continue to react for 15 minutes at reflux. It was then neutralized with 8 g of glacial acetic acid and diluted with 350 ml of benzene. After the reaction solution cooled, it was washed with two portions of water of 75 and 20 ml respectively. The combined aqueous phases were extracted with 50 ml of benzene twice to give a solution in benzene which was combined with the chief portion, dried with Na2SO4 and concentrated in a rotary evaporator. Distillation yielded 118.5 g of a first fraction of b.p. 46°-68° C./8 mm Hg, which largely consisted of diethyl phosphite, and 280.8 g (85.6% of theory) of the oxaphospholane which boiled at 122°-132° C. at 0.008 mm Hg. Gas chromatography showed the product to be about 95% pure. 8.2 g remained as the distillation residue.

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