Реакция #83731

Уравнение реакции

oxalic acid dimethyl ester

n-butyllithium

diisopropylamine

hydrochloric acid

(R)-3-hydroxybutyric acid methyl ester

→

(R)-2-hydroxy-3-methoxycarbonyl-2-penten-4-olide

Растворители

ethyl acetate

n-hexane

tetrahydrofuran

Условия реакции

Обработка

1. 1
   Другоеpre-purified by extraction into aqueous bicarbonate solution, acidification with 6N hydrochloric acid to pH 2.5 and extraction once more with ethyl acetate
2. 2
   workup.DISTILLATIONThe solvent is distilled off
3. 3
   Другоеthe residue is recrystallised from ether/petroleum ether
4. 4
   Другое[α]D20 =+30.0° (3% in CHCl3), m.p. 94°-96° C.

Методика

775 ml of 1.6M n-butyllithium solution in n-hexane are added dropwise within a period of 20 minutes at -25° C. to a solution of 1.27 mol of diisopropylamine in 600 ml of tetrahydrofuran. At -70° C., 70.9 g of (R)-3-hydroxybutyric acid methyl ester are then added dropwise within a period of 30 minutes and, after 1 hour, 70.9 g of oxalic acid dimethyl ester are added dropwise within a period of 40 minutes. After a reaction time of two hours at -60° C., the whole is warmed to 0° C. and acidified to pH 2 with 430 ml of 6N hydrochloric acid. The product is isolated by repeated extraction with ethyl acetate and pre-purified by extraction into aqueous bicarbonate solution, acidification with 6N hydrochloric acid to pH 2.5 and extraction once more with ethyl acetate. The solvent is distilled off and the residue is recrystallised from ether/petroleum ether. [α]D20 =+30.0° (3% in CHCl3), m.p. 94°-96° C.

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