SU1237666A1 - Method of producing 2,2-dimethyl-4,6-dioxo-1,3-dioxane - Google Patents

Description

The invention relates to an improved process for the preparation of 2 ,, 2-dimethyl-4,6-dioxo-1, 3-dioxane (Meldrum acid), which is widely used in fine organic synthesis and the production of natural compounds and medicinal preparations.

The purpose of the invention is to intensify the process and increase the yield of the desired product by removing the acetic acid formed and thereby reducing the acidity of the medium and carrying out the process at a low temperature, which prevents the hydrolytic decomposition of the 1,3-dioxane ring from reverse reaction.

PR m and m 1

Conducting condensation at + 25 ° С without preliminary removal of acetic acid. To a suspension of 20.8 g (0.2 mol) of finely ground malonic acid in 25 ml (0.27 mol) of distilled acetic anhydride, was added Yu, 5 ml of concentrated sulfuric acid, the mixture was stirred until the malonic acid was dissolved, to the resulting solution at + 2.5 ° C, 16 ml (0.22 mol) of anhydrous acetone was added and left overnight (15 hours). Fallen yellowish crystals. filtered, washed with cold water (2 x 10 ml), from the mother liquor after re-cooling, filtering and washing, an additional amount of the substance was obtained. The total yield of yellowish crystals of Meldrum acid after drying in a desiccator is 12 g (42%). To obtain a colorless preparation, the substance was precipitated from a solution in acetone of water.

. Output 8.5 g Example

(15 ml) two times the amount (30%) of mp.92-93 0 2. Conducting the process. condensation at 15 hours with preliminary removal of acetic acid and excess acetic anhydride.

0.5 ml of concentrated sulfuric acid was added to a mixture of 20.8 g (0.2 mol) of malonic acid and 70 ml (0.74 mol) of acetic anhydride, stirred for 10 minutes until the malonic acid was completely dissolved and left at 1 h at

. Excess acetic anhydride

target

and acetic acid was distilled off under vacuum of 1 mm Hg at + 60 ° C to the obtained reaction mixture (yellow) while 20 ml (0.27 mol) of anhydrous acetone was added during 20 minutes (the mixture acquired a dark yellow color) and left overnight. After isolation and purification

the reaction product as in example 1 was obtained 13 g

(46%) of colorless acid Meldrum from about.

t pl - P

92-93 S. r and me

Carrying out the process at O C with acetic acid distillation immediately after mixing the reagents.

To a mixture of 26 i: (0.25 mol) of malonic acid and 53 ml (0.56 mol) of distilled acetic anhydride, 5 drops of concentrated sulfuric acid were added, stirred for 10 minutes until the majority of the malonic acid was dissolved (the reaction mixture cooled), acetic acid and excess acetic anhydride were distilled off for an hour while

in a vacuum of 1 Hg. To balance about.

+ 15 ° С

20 ml (0.27 mol) of anhydrous acetone were added during 5 minutes with stirring and the colorless reaction was cooled, the ionic mixture was cooled to -10 ° C. After an hour, the crystals were filtered off, washed on the filter with ice water (2x15 ml), mother liquor the solution was cooled again and, after a similar treatment, isolated and an additional amount of Meldrum acid; both of them were dried in a desiccator over KOI and obtained 24.8 g

(77%) of colorless crystal Sichen with t, pl. 92-94 S.

PRI me R 4. Carrying out the reaction at -10 C as in Example 3.

After the removal of acetic acid, acetone was added for 5 g-gin with and further processed as in Example 3, Vjod Meldr: 76%

. pl,

92-94 ° C.

55

. Equivalent to neutralization: 143.6; 144.4. €,

Calculated 144,12. IR spectrum, cm (0.03 mol) liter: 976 (70), 1016 (50), 1085 (53), J269 (35), 1308 (37), 1355 (30), 1396 (35);

31

1606 (19), 1756 (90), 1785 (70), 2925 (13) 3005 (16), 3070 (22),

Spectrum PMR S, ppm, (acetone d 6, 0.3 mol (l): 1.80 (bN, s, 2CH), 3.92 (2H, s CH2).

As can be seen from the results given in examples 1-4, these advantages of this method make it possible to reduce the total process time by at least 5-6 times, to reduce almost twice the consumption of acetic anhydride and at the same time to increase the yield of the target product by 30-35% reactions, i.e. 1.7 times, compared with the known method.

With a strong decrease in temperature (down to -50 ° C), glass transition is observed, partial crystallization of the reaction mixture and as a result of the reaction in a heterogeneous medium, the yield of the target product decreases sharply

6664

Example5. To a mixture of 31.2 g

(0.3 mol) of malonic acid powder and 65 ml (0.68 mol) of distilled acetic anhydride added 5 drops of conc. sulfuric acid, stirred for 10 minutes until the majority of the malonic acid was dissolved. Acetic acid and excess acetic anhydride were distilled off within an hour.

under vacuum at 1 mm Hg. to the residue for 10 minutes at -3 ° C and stirring with a magnetic stirrer to obtain 18.6 g (0.32 mol) of anhydrous acetone, while

partial crystallization of the reaction

mixture, after 2 h, the mixture was transferred to a filter, the crystalline precipitate was filtered,. rinse with ice water (2x15 ml) and then treat as in the example. The yield of Meldrum acid is 10.2 g (36%), m.p. 86-9G.

Claims (1)

METHOD FOR PRODUCING 2,2-DIMETHYL-4,6-DIOXO-1,3-DIOXANE by condensation of malonic acid with acetone in the presence of acetic anhydride in the presence of sulfuric acid, characterized in that, in order to intensify the process and increase the yield of the target product, after mixing malonic acid. With acetic anhydride and sulfuric acid, the resulting acetic acid is removed and the condensation is carried out at a temperature of 0 to 10 ° C. yo oo m