CS235379B1 - Method of 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydro-pyrimidine preparation - Google Patents

Abstract

The present invention provides the preparation of 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine (called also acetonine) in the absence of a catalyst or a promoter under elevated pressure 0.2 to 6.0 MPa and temperatures of 30 to 130 ° C. Acetone is used as an intermediate to prepare the trlacetonamine from which it is further) a variety of stabilizers can be prepared synthetic polymers with excellent effects or serves as an intermediate for the preparation of pharmaceutical preparations. The process of the invention is simplified technological process, improves living environment, saving economic resources before, the team spent on needed catalysts or promoters.

Description

The invention relates to a process for the preparation of 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine in the following, called acetonine, by reacting acetone with ammonia in the absence of a catalyst or promoter at elevated temperature and pressure.

Acetone is used to prepare triacetonamine from which a variety of stabilizers of synthetic polymers can be prepared. These stabilizers have excellent performance especially when used in outdoor applications. Therefore, the demand for both triacetonamine and ocetonone is increasing.

Acetonine is known to be formed in the reaction of acetone with ammonia in relatively high yields when the reaction is carried out in the presence of acid catalysts, generally Lewis acids and promoters. Catalysts and promoters include various inorganic and organic salts (Brandbury RB et al., J. Chem. Soc. 1947, 1394-99), ion exchangers (US Patent 3,984,625), montmorillonite minerals (German Patent No. 1,276,041), or halo, genes and compounds thereof (U.S. Pat. No. 3,943,134). A continuous process for the production of acetonine and its subsequent isolation is also known (German Patent 1 276 041).

The prior art process for the preparation of acetonine from acetone and ammonia in the absence of catalysts is neither preparative nor industrially applicable, as it yields only 17 ° / o acetone yield over 7 days at a reaction temperature of 25-30 ° C and depressurized (Bradbury R, B. et al., J. Chem. Soc., 1947, 1394-1399). All other processes have the disadvantage that a catalyst is used in the preparation of acetonine, which must either be removed during the treatment or regenerated from time to time or replaced in the reaction apparatus.

It has now been found that acetonine can be prepared in the absence of a catalyst or promoter from acetone and / or diacetomyl alcohol and / or mesityl oxide at an elevated pressure of 0.2 to 6.0 MPa and a temperature of 30 to 130 ° C.

Acetone is formed in this preparation process in relatively high yields for the introduced acetone in an amount of 60 to 85%. If desired, liquid anhydrous acetonine or crystalline monohydrate may be isolated from the reaction mixture by fractional distillation under reduced pressure, possibly by crystallization of acetonine monohydrate after salting off excess water.

The process of preparing acetonine directly from acetone and ammonia in the absence of any catalyst greatly simplifies the entire process. The reaction can be conducted either discontinuously or continuously as desired. The catalyst required for the synthesis according to the known processes is saved. Further, in the process of the present invention, there is no need to regenerate the catalyst or remove it from the reaction medium. The reaction is very fast and a yield of 60-85% yield on acetone loaded is achieved in 4 hours. Catalyst residues, which are almost always transferred to the next stage of the process, do not complicate the technological process and do not introduce distillation or filtration devices.

The present process produces an equimolar amount of water that can be left in the reaction medium and does not affect most of the other syntheses. In the case of isolation of pure acetonine, water can be easily removed by rectification or by salting out the water and separating the upper, organic layer of acetonin.

The reaction may be carried out at a temperature of 30 to 130 ^Q C, preferably at 70 to 120 ^DEG C. and a pressure of from 0.2 to 6 bar, preferably at 0.8 to 4.0 MPa. It is also preferred to use an excess of ammonia to acetone over equimolar ratios. The molar ratio of acetone to ammonia ranges from 1: 0.55 to 1: 3, preferably 1: 0.7 to 1: 2.

The reaction according to the above procedure produces a homogeneous mixture and eliminates any phase separation, or does not produce any polluting waste.

The following examples illustrate the invention without limiting it.

Example 1

116.0 g (2 mol) of acetone and 22.66 g (1.33 mol) of ammonia were charged to a 250 ml metal pressure reactor with duplicator and the reaction mixture was heated to 100 ° C. The reactor pressure was maintained at 1.3 MPa. After 4 hours, the reactor was cooled and an oily acetonine oil solution was obtained which was suitable for further synthesis. Acetone yield 51.2%, acetone conversion 72.5%, acetone to acetonine selectivity 70.6%. Acetone: ammonia molar ratio 1: 0.66.

Example 2

116 g (2 mol) of acetone and 34 g (2 mol) of ammonia were charged to a metal pressure reactor and the reaction mixture was heated to 100 ° C. The reactor pressure was maintained at 2.1 MPa. After 4 hours, an oily acetonine solution was obtained from the cooled reactor. Acetone yield 58.9%, acetone conversion 83.5%, acetone selectivity to acetonine 70.5%. 1: 1 acetone: ammonia molar ratio.

EXAMPLE 3 g (1 mol) of acetone and 22.1 g (1.3 mol) of ammonia were introduced into a metal pressure reactor and after 4 hours at 100 DEG C. and a pressure of 2 bar, an oily acetonine solution was obtained. Acetone yield 54.8%, acetone conversion 74.7%, acetone to acetonine selectivity 73.4%. Acetone: molar ratio

: ammonia 1: 1.3.

Example 4 g (1 mol) of acetone and 22.1 g (1.3 mol) of ammonia were charged to a metal pressure reactor. The reaction mixture was heated to 120 ° C and the pressure was maintained at 3.3 MPa. After 4 hours after cooling the reactor, a oily oily acetonine solution was obtained. Acetonine yield 76.4%, acetone conversion 85.8%, acetone selectivity to acetonine 89.0%. Acetone: ammonia molar ratio 1: 1.3.

Example 5

116 g (2 mol) of acetone and 68 g (4 mol) of ammonia were charged to a 600 ml pressure metal reactor. The reaction mixture was heated to 100 ^° C and the pressure was maintained at 3.8 MPa. After 4 hours from the cooled reactor, an oily acetonine solution was obtained. Acetone yield 83.2%, acetone conversion 92.4%, acetone to acetonine selectivity 90.1%. 1: 2 acetone: ammonia molar ratio.

example

58 g (1 mol) of acetone and 34 g (2 mol) of ammonia were charged into a metal pressure reactor. The reaction mixture was heated to 120 ° C and the reactor pressure was maintained at 4.2 MPa. After 4 hours, the reactor was cooled. An oily liquid of acetonine was obtained. Acetone yield 91.2%, acetone conversion 96.8%, acetone selectivity to acetonine 94.2 percent. 1: 2 acetone: ammonia molar ratio.

Example 7 g (1.5 mol) of acetone and 51 g (3 mol) of ammonia were charged to a metal pressure reactor. The reaction mixture was heated to 100 ° C and the pressure was maintained at 4.4 MPa. After 4 hours, the reactor was cooled and an oily acetonine solution was obtained. Acetonine yield 86.3%, acetone conversion 90.3%, acetone to acetonine selectivity 91.2%. 1: 2 acetone: ammonia molar ratio.

Example g of acetone (lmolj and 51 g (3 mol) of ammonia was charged to a pressurized reactor. The mixture was heated to 130 ° C, kept at a pressure of 4.8 MPa. After 4 hours the reactor was cooled. acetonine yield 92.8%, acetone conversion 97.2%, acetone selectivity to acetonine 95.5% molar acetone: ammonia ratio 1: 3.

Example 9

116.2 g (1 mol) of diacetone alcohol and 28.2 g (1.6 mol) of ammonia were charged to a metal pressure reactor and heated to 100 ° C at a pressure of 2.8 MPa. The reactor was cooled after 4 hours. Similar to the previous cases, an oily acetonine oil solution suitable for further syntheses was obtained. Yield. acetonine 70.1%, diacetone alcohol conversion 81.4%, selectivity 86.2%. Example 10

49.6 g of mesityloxide (0.5 mol), 58.1 (0.5 mol) diacetone alcohol and 34 g (2 mol) ammonia were charged to a 'metal pressure' reactor and heated to 90 ° C while maintaining the pressure at 90 ° C. After 4 hours, the reactor was cooled and an oily acetonine solution was obtained: acetonine yield 69.96%, conversion 82.6%, selectivity 84.7%.

EXAMPLE

99.2 g (1 mol of mesityloxide and 28.22 g (1.6 mol) of ammonia were charged to a metal pressure reactor. The reaction mixture was heated to 100 ° C and the pressure in the reactor was maintained at 2.9 MPa. the reactor was cooled and an oily acetonine solution was obtained, acetonine yield 61.6%, conversion 75.8%, selectivity 81.3%.

A 11 g / h (0.18 mol) acetone and 6.4 g / h (0.37 mol) ammonia were charged to a flow reactor equipped with a duplicator using a pressure pump so that the residence time in the reactor was 4 hours. The reactor was heated by a thermostatic unit to 100 ° C and the pressure in the reactor was maintained at 4.0 MPa. A yellow oil, similar to the previous examples, was obtained from the reactor and contained acetonine in a yield of 78.3%.

Example 13

As in Example 12, acetone and ammonia were fed to a flow pressure reactor which was tempered to 120 ° C and the pressure maintained at 4.5 MPa. The obtained oily acetonine solution contained acetonine in a yield of 85.4%. 1: 2 acetone: ammonia molar ratio.

Claims (3)

SUBJECT Process for preparing 2,2,4,4,6-pentamethyl-2,3,4,5-tetrahydropyrimidine, characterized in that acetone and / or diacetone alcohol and / or mesityloxide are reacted with ammonia at an elevated pressure of 0.2 to 6, 0 MPa and temperatures of 30 to 130 ° C.