SU883039A1 - Method of preparing 5,6-dihydro-(2h)-pyrans - Google Patents

Description

This goal is achieved by the fact that a diene of the general formula R2-CH c-CH CHa (l where fti and have the above meanings, is condensed with formaldehyde in the presence of a mineral acid or cation exchange resin in the H form at 85-100 ° C and the molar ratio of diene: formaldehyde equal to 1: 1-0, 2. The yield of the target product is 70.090, 3%. The initial formalin (37% aqueous formaldehyde solution), isoprene, divinyl are produced on an industrial scale, piperylene is a non-utilizable waste of large-scale production of isoprene rubber. mineral ki slots can be used solutions of sulfuric, hydrochloric or phosphoric acid in formalin, and as a cation-exchange resin in the H form, KU-2. Synthesis of 5,6-dihydro (2H) pyranes is carried out under static or continuous conditions. In the first case, a vessel made of a non-magnetic material (for example, stainless steel IXl.SHlOT) is used in the form of a cylinder equipped with a heating jacket and an airtight lid. Thermostated liquid is pumped through the jacket from a thermostat. The process is carried out in the next sequence. A pre-prepared solution of acid in formally is poured into the vessel (the ratio of reagents is shown in Table 2) and 0.5 mol of diolefine is poured, the lid is closed, the vessel is placed on a magnetic stirrer, creating an intensive mixing of the phases. After a set time (2.5-5.5 hours), the magnetic stirrer is turned off, the contents of the vessel are cooled by supplying cold water to the jacket, the vessel is opened, the layers are separated and from the upper organic layer after neutralization with aqueous ammonia solution, the evaporation is separated. , 6-dihydr6- (2H) pyrans. The lower aqueous layer containing unreacted formaldehyde is separated and, after strengthening, rotated into the reaction. In order to synthesize 5,6-dihydro (2H) pyranes, a flow system consisting of a metal reactor equipped with a heating head, a dosing pump, a pressure regulator, raw burettes, a thermocouple installed in the reactor, a potentiometer, refrigerator and sink. The reactor is filled with KU-2 cation-exchange resin in the H form. The experiments were carried out in the following sequence. Regarata from the raw burettes are taken up by pumps and fed to the reactor. Pre-establish the corresponding costs of reagents (Table 3). The pressure regulator maintains in the system at least 7-8 kg / cm (for carrying out the reaction in the liquid phase) by throttling the flow by means of a valve installed at the outlet of the reactor. The reaction products are then cooled in a refrigerator and collected in a receiver. The reaction mass consists of 2 layers. Lyran is isolated from the upper organic layer after neutralization with ammonia by single evaporation. In addition to pyrans, compounds containing compounds whose constants are given in Table 1 were isolated and identified from the reaction mass of condensated dienes with formaldehyde in an acidic environment. For identifying 5,6-dihydro (2n) pyranes and other compounds, they used UV, IR, PMR spectra. The method is illustrated by the following Examples. P i and m 1. From 27.0 g of divinyl and 4.5 g of formaldehyde (in 37% aqueous solution) under static conditions (temperature, synthesis time 3 hours, the concentration of sulfuric acid in 5% by weight), according to the procedure described above, 6 34 g of 5,6-dihydro (2H) -pyran. Pyran yield, wt.%, Divinyl conversion, 17.0 wt.%. Constants of 5,6-dihydro (2H) -pyran: b.p. 1.4438; df 0.8215. MRo calculated 24.27; found 24.20. Found,%: C 71.49; And 9.61. .SVN, OO. . Calculated,%: C, 71.42; And 9.52. Approximately 2. Of 34.0 g of piperylene and 4.5 g of formaldehyde (in 37% aqueous solution) under static conditions (temperature, synthesis time 3.5 hours, sulfuric acid concentration 5% by weight) using the procedure described above. 8.32 g of 2-methyl-5,6-dihydro- (2H) -pyran are obtained, the yield of pyran is 90.3 wt.%, Piperylene conversion is 18.8 wt.%. Constants of 2-methyl-5,6-dihydro- (2H) -pyran: b.p. 104 ° C; RP l, 4329; dj, 0.8794. Mo calculated 28.89; found 29.03 Found: C74.13, H 10.75 CbH, oO. Calculated,%: C 73.56; H 10.28. Example 3. From 68.0 g of piperylene and 9.0 g of formaldehyde (in the form of technical formalin) under continuous conditions (temperature, weight feed rate of piperylene 0.2 g / g KU-2 per hour) using the above procedure, 36.8 g are obtained 2-methyl-5,6-dihydro-C2H) pyran. The yield of pyran is 87.3 wt.%, Piperylene conversion is 43.0 wt.%. The constants of the isolated 2-methyl-5,6-dihydro- (2H) -pyran are in good agreement with the constants given in example 2. Example 4. Of 68.0 g of isoprene and 15, O g of formaldehyde (in the form of technical formalin) under continuous conditions (temperature, esov feed rate of isoprene, 0.2 g / g CU.-2 per hour), according to the above-described meedex, 22.2 g of 4-methyl-5,6-dihydro- (2H) .- pyran is given. The output of pyran is 53.4 wt. L, isoprene conversion of 42.1 wt.%. Constants 4-methyl-5,6-dihydro- (2H) pyrana. Bp 119.C; nS l, 4497; d 0.9060. MKD calculated 28.89; found 29.08. Found,%: C 74.13; H 10.75. SbN, (p. Calculated,%: C 73.56; H 10.28. The proposed method allows to obtain 5,6-dihydro- (2H) pyranes based on readily available petrochemical products produced in industrial output (up to 90.2 e.%).

4-Vi.nil-1,3-dioxan

1,3,7-Trioxaper .hydronaphthalene

4-penten-1,3-diol 4-propenyl-1,3-dioxane

6-Methyl-1,3,7-trioxperhydronaphthalene

4-Methyl-4-vinyl-1, 3-dioxane

a 6 l and c a i

1,4444 0,9981

CfiH oOj143,5

.jO, 47.5 (pl)

ССН, „0 98/6 mm Hg 1.4630 1.0021

5 10 Z

1.4520 0.9837

 170.0

CHICOP 52 (pl)

1.4442 0.9790

MO D: F - molar ratio diene: formaldehyde

table 2

Table 3

Claims (1)

Claim A method of obtaining 5,6-dihydro- (2H) ~ ⁴⁰ pyranes of the general formula of a cation exchange resin in D * * form at elevated temperature, characterized in that, in order to increase the yield of the target product, cess is carried out at 85-100 ° C and molar the ratio of diene and formaldehyde equal to 1: 1-0.2.