CS269409B1 - Applies to the Pneumatic Tightening Unit Sensor Tightening Screw, Nuts and the like, with the possibility of adjusting the torque sieve and turning the drive unit off when reaching the set torque sieve. It brings improved coordination of the work of individual spindles in multi-spindle tightening devices. Its essence lies in it. that the sensing arm at the free end is ductile ended with a parallel surface serving as sensing surfaces, and the sensor holder is provided with a passage for positioning the sensors. - Google Patents

Abstract

A general method for the preparation of esters of dialkylaminoacrylic acid of the general formula CHo=C.C00R * I η o where R is a primary, secondary or tertiary alkyl or aralkyl with one to nine carbons and the groups Ri and R2 are either the same or different, namely alkyls or aralkyls with one to nine carbons or together form a five to seven-membered ring containing a nitrogen atom or a nitrogen and oxygen atom. The described method is based on esters of pyruvic acid, which are converted into the desired products by reaction with a reagent obtained from the corresponding amine and an inorganic halide, in such a way that the reaction mixture does not contain free amine. The products are potential drugs, insecticides, complexing agents and others. In addition to their undeniable technical importance, they can also be used in the theoretical field.

Description

The invention provides a general method for preparing esters of -dialkylaminoacrylic acid. -Dialkylaminoacrylates of the general formula ch ₂ =c.coor

1(5¼ ² where 5 is a primary, secondary or tertiary alkyl or aralkyl of up to nine carbons and the groups B ¹ and S ² are either the same or different, namely alkyls or aralkyls of up to nine carbons or together form a five to seven-membered ring containing a nitrogen atom or a nitrogen and oxygen atom, have not been studied at all, although their structural elements - the enamine group together with the ester function - make these compounds very attractive intermediates of organic synthesis. These substances are also remarkable from a _theoretical point of view. A unique derivative of this group, methyl piperidineacrylate, was prepared in connection with the study of captodative olefins, i.e. olefins carrying both an electron-donor and an electron-acceptor group on the same carbon atom of the double bond. The mentioned compound was isolated in low yield (5 to 10 $) as one of the products of the reaction between methyl chloroacrylate and piperidine (8. Mignani, Z. Janoušek, 5. Merenyi and HG Viehe, J. Riga and J. Verbist, Tetrahedron Lett, 25. 1571-1574 /1984/)· The lack of suitable methods for their preparation has so far hindered the deeper study of these compounds.

The availability of dialkylaminoacrylates is the subject of the present invention, a method for preparing Z-dialkylaminoacrylic acid esters, the essence of which is that to an amine of the general formula R ¹ E ² NB, where the substituents R ¹ and K ² have the same meaning as above, dissolved in an inert solvent, at temperatures in the range of +20 to -30 °C, at least a stoichiometric amount of a chloride selected from the group comprising aluminum chloride, arsenic chloride, titanium chloride and tin chloride is added, then to this reaction mixture is further added pyruvic acid ester of the general formula CHjCO.COOR, where 5 has the same meaning as above and the product is isolated in a conventional manner.

The general method of synthesis of Z-dialkylaminoacrylates, described in this invention, is based on pyruvic acid esters. In the course of the described process, it is necessary to convert the CH^CO group of the starting ester to an enamine. As is known, pyruvic acid esters (pyruvates) are extremely easily subjected to both hydrolysis and a number of other nucleophilic reactions, including condensation reactions. The condition for their conversion to the desired esters is therefore the maintenance of mild reaction conditions and, in particular, the absence of a free amine, which could convert the ester function to an amide function. This requirement eliminates the use of most methods suitable for the synthesis of enamines.

The synthesis procedure for _< /-dialkylaminoacrylates according to the invention was based on the findings described by While and Weingarten (J. Org. Chem. J2, 213 /1967/). These authors found that many ketones, including sterically hindered ones, can be converted into enamines by reaction with amines in the presence of some inorganic chlorides, mostly tri- and tetrachlorides, of which TiCl^ - titanium tetrachloride - proved to be the best. In order to convert sensitive pyruvic acid esters into the corresponding enamines -</-dialkylaminoacrylates - it was necessary to modify the reaction arrangement and its conditions, primarily so as to prevent contact of pyruvate with the free amine. This was achieved by first adding such an amount of chloride to a solution of the corresponding amine in an inert solvent that the chloride remained in a slight stoichiometric excess. The basic stoichiometry of this process is further illustrated by two examples, the first of which relates to the use of tetrachloride, the second to trichloride:

CH ₃ CO.COOR + 6 (CH ₃ ) ₂ NH + TiCl ₄ = 2 CH ₂ =C.COOR + 4 (CH-j) ₂ NH,BC1 + TiO ₂ n(ch ₃ ) ₂

C8 269 409 Bl

CHjCO.COOR + 9 (CHjJgNH + 2 AsCl-j = 3 CH ₂ =C.COOB + 6 (CH-jJ^.HCl + As ₂ 0 ₃ k(CH ₃ ) ₂

A large number of inorganic tri- and tetrahalides can be used for this method, namely elements belonging to groups IIIA, IV and VA of the periodic table, while the quality and yield of the product depend significantly on the nature of the halide used. For example, TiCl^, which is recommended (see White and Weingarten) as the most effective halide for the synthesis of enamines, gives a worse result in the case of pyruvates than, for example, AsClj, which is a less reactive halide. This can be explained by the already mentioned high sensitivity of pyruvates to various reagents. This sensitivity also requires careful performance of the reaction, especially the observance of moderate temperatures, preferably in the range of +15 to -30 °C.

The described reaction can be carried out in essentially any inert solvent, for example in saturated and aromatic hydrocarbons, chlorinated solvents, etc. It is possible to work with great advantages in dry ether, especially in cases where the product is low-boiling. Isolation of the products is simple in all cases. The by-products of the amine salts together with the oxides are filtered off with suction and the product is isolated by rectification or crystallization.

The present invention is further illustrated by the examples, which, however, do not limit it in any way.

Example 1 Methyl o6-Dimethylaminoacrylate

A solution of 67.6 g (1.? mol) of dimethylamine in 600 ml of dry ether was introduced into a 2 l three-necked flask equipped with a stirrer, dropping funnel and thermometer. While stirring and external cooling, a solution of 60.4 g (28 ml, 1/3 mol) of arsenic trichloride AsC1 ₃ in 200 ml of ether was added over a period of about 30 min at a temperature of -20 °C. The reaction mixture was stirred for another 30 min and then again at a temperature of -20 °C a solution of 51.05 g (0.5 mol) of methyl pyruvic acid ester in about 100 ml of ether was added dropwise over a period of about 20 min. Stirred without cooling until the temperature reached room temperature and left until the next day. The precipitate was filtered off with suction, washed with 3x100 ml of dry ether, the solution obtained was filtered through a small column of silica gel and the ether was distilled off through a column under very gentle vacuum. The product was isolated by rectification; 53.6 g (83% methyl-dimethylaminoacrylate) was obtained, boiling at 48-51.5 °C/9 Torr. ^X H NMR (CDCl-j): 5.05s (1 H); 4.43s (1 H); 3.78s (3 H); 2.63s (6 H).

Example 2 / -Methyl morpholinoacrylate

In the same apparatus as in Example 1, a solution of 19 g (0.1 mol) TiCl^ in 60 ml cyclohexane was added dropwise to a solution of 52.3 g (0.6 mol) of morpholine in 250 ml of a cyclohexane-benzene mixture (1:1) at -25 °C. After 30 min of stirring, a solution of 20.4 g (0.2 mol) of methyl pyruvic acid ester in 60 ml of benzene was added dropwise at -25 °C. Stirred without cooling for about 4 hours, left until the next day. The precipitate was sucked off, washed well with a benzene/cyclohexane mixture and the solution was filtered through a layer of silica gel. The solvents were removed in vacuo. 20.8 g of the residue were obtained, which crystallized after cooling. The yield of the product, methyl c<-morpholinoacrylate, corresponds to 60.8%. The substance can be crystallized at low temperatures (-30 °C) from ether, mp 46 to 49 °C. NMR (CDCl ₃ ): 5.26s (1 H); 4.63s (1 H); 3.79s (3 H); 2.98 - 3.92m (4 H); 2.82 - 3.0m (4 H).

Example 3 Methyl morpholinoacrylate was prepared by the same procedure as in Experiment 2, except that SnCl2 (26 g, 0.1 mol) was used instead of TiCl2. The product was obtained in a yield of 68%.

CS 269 409 Bl

Example 4 Methyl o-morpholinoacrylate was prepared by the same procedure as in Example 1, except that an equivalent amount of AlCl2 was used instead of ZeCl2. Yield

%.

Example 5 Methyl morpholinoacrylate was prepared by the same procedure as in Example 1 except that morpholine (130.7 g, 1.5 mol) was used in place of dimethylamine. The crystalline product was obtained in a yield of 92%.

Example 6.

t/-Methyl piperidinoacrylate

The procedure was the same as in Example 1, with the difference that piperidine was used as the amine and the operation was carried out at a temperature of +20°C. 75% of the desired product was obtained with a b.v.

°C/0.5 Torr. ^Χ Η NMH (CDCl 1 ): 5.11a (1 Η)| 4.5e (1H){ 3.78s (3H); 3.0 - 2.?m (4H);

1.8 - 1.4m (6 H). ’

Example 7 Methyl cZ-Pyrrolidinoacrylate

The procedure was the same as in Example 1 b, except that pyrrolidine was introduced into the reaction as the amine. By distillation, a fraction boiling at 59 to 61 °C/1 Torr was isolated in a yield of 10%. ^X H NMR (CDCl ₃ ): 4.73β (1 H); 4.16a (1 H); 3.78s (3 H); 3.3 - 2.98m (2 H); 2.0 l.74m (2 H).

Example 8 cZ- t-butyl dimethylaminoacrylate

The desired product was obtained in a yield of 75% by the same procedure as in Example 1. Bp 72.5 to 74.5 °C/11 Torr. ^1H NMH (CDCl 3 ): 4.87a (1 H); 4.45a (1 H); 2.62s (6 H); 1.55s (9 H).

Example 9 ·

-Isopropyl morpholinoacrylate was prepared by the same procedure as in Example 2, with the difference that instead of methyl pyruvic acid ester, isopropyl pyruvic acid ester was added to the reaction.

The product was obtained in a yield of 55%.

Esters of Z-dialkylaminoacrylic acid provide organic synthesis with wide possibilities. They can undergo a number of electrophilic substitution reactions typical of enamines (acylation, reactions with carbonyl compounds, etc.) as well as for captodative olefins (see the above-mentioned reference by the authors S. Mignani et al.). The field of cycloaddition reactions provides remarkable possibilities, whether within the framework of Diels-Alder type reactions or ^2+2j cycloaddition reactions to form compounds with a four-membered, i.e. cyclobutane ring. Many of the products of the above reactions are potential drugs, insecticides, complexing agents, etc. In addition to their undeniable technical importance, they can also be applied in the theoretical field.

Claims (1)

SUBJECT OF THE INVENTION Method for preparing esters of (/-dialkylaminoacrylic acid of the general formula CH,=C.COOR ¹ 1 2 CS 269 409 Bl where B is a primary, secondary or tertiary alkyl or aralkyl of β to nine carbon atoms and the groups R and R are either the same or different, namely alkyls or aralkyls of β to nine carbon atoms or together form a five to seven membered ring containing a nitrogen atom or a nitrogen and oxygen atom, characterized in that to an amine of the general formula B^ R ² NH, where R ¹ and B have the same meaning as above, dissolved in an inert solvent and at temperatures in the range of +20 to -30°C is added at least an at least stoichiometric amount of a chloride selected from the group comprising aluminum, arsenic, titanium and tin chloride, then to this reaction mixture is further added a pyruvic acid ester of the formula CH^CO.COOR, where B has the same meaning as above and the product is isolated in a conventional manner.