DE1770454A1 - Process for the preparation of substituted oxazolones - Google Patents

Description

Process for the preparation of substituted oxazolones It is known that acylaminocarboxylic acids can be cyclized to the corresponding oxazolones by means of compounds which split off water, preferably acetic anhydride9. The reaction proceeds according to the following equation When R is a group having a polymerizable double bond, e.g. B. a vinyl or isopropenyl group, and R1 and R2 are lower alkyl radicals, polymerizable oxazolones can be produced according to this scheme, which are used for the production of crosslinkable polymers Application areas too expensive.

It has now been found that the cyclization can also be carried out in the absence of dehydrating agents by using compounds of the general formula where R1 and R2 are lower alkyl radicals or when taken together with the adjacent carbon atom form a carbocyclic ring, R3 is an alkyl or alkenyl radical and R is hydrogen or a lower alkyl radical, finely divided or in a thin layer heated to temperatures above 200 ° C. The ring bottom reaction ends particularly smoothly when at least one of the radicals R1 and R2, but preferably both, are methyl groups. If the radical R3 is a lower alkenyl radical, such as. B. is a vinyl, isopropenyl or allyl group, polymerizable oxazolones are obtained. The same oxazolones can be prepared from suitable saturated intermediate products, which in turn can be prepared by the process according to the invention. If, for example, the acylaminocarboxylic acid R3 used is a 2-chloro-isopropyl radical or an acetoxyethyl radical, an unsaturated polymerizable radical can be produced from the corresponding oxazolone by elimination of hydrogen chloride in one case and thermal acetic acid elimination in the other.

The implementation of acylaminocarboxylic acids has the greater practical More important than that of the acylaminocarboxylic acid alkyl esters, since the former are technical are more easily accessible. In some cases, however, the esters starting out, achieve better yields.

The method of the invention can be carried out in various ways be, the starting material in a dtirmer layer or in fine distribution are used uB.

The expression "in fine distribution" is intended to include all embodiments include where the starting material is either in molecular distribution, such as in solution or in the vapor state, or in the form of small droplets in intimate contact heated with another liquid or gaseous phase will. In order to avoid losses due to decomposition, the heating should not be essential take longer than is necessary for complete implementation.

A simple embodiment of the method is the liquid or molten starting material in a heated tube filled with fillers to drop in. The implementation then occurs in a thin layer on the filling bodies or in the vapor phase. You can also use the liquid or molten starting material or its solution in a suitable solvent in a thin layer over heated Allow pipe walls and the like to run down. If the reaction is in solution in emulsion or dispersion carried out, the reaction can be carried out when passing through a heated Drain tube or a tube bundle reactor. As a solution, emulsifier or. Dispersing medium Any liquid that does not interfere with the reaction can be used. It is particularly advantageous to work under a negative pressure at which the formed Oxazolone evaporated and separated from the reaction mixture via the gas phase can. Liquid distributing agents suitable for this procedure are, for. B.

Silicone oils, high-boiling hydrocarbons, chlorinated aromatics, Dioxane or dimethylformamide.

In principle, in all embodiments of the method, the continuous operation preferred because of the short heating times possible. In the case of a batchwise procedure, the yields are generally lower.

The oxazolones obtained react with compounds having a reactive hydrogen atom, hereinafter referred to as XH, with ring opening to form linear addition products according to the equation wherein R1, R2 and R3 have the meaning given earlier.

They are therefore available in a variety of ways as organic intermediates can be used, in particular those products of the process in which R3 is a polymerizable group is used for the production of polymers, the pach the above scheme with bifunctional compounds, such as primary aliphatic Diamines, are crosslinkable.

Example 1: 60 g of methyl N-methacryloyl-aaminoisobutyrate stabilized with 0.5% hydroquinone (Melting point 98-990 c) as a melt within 30 minutes at 15 Torr by a vertical one with Raschig rings, stainless steel coils or 40 cm long tube filled with coarse-grained quartz and heated to 220 - 2300 C and 4 cm in diameter. The reaction mixture emerging in gaseous form at the lower end of the tube is condensed in a cooler.

Distillation of the condensate at 12 torr gives 2-isopropenyl-4,4-dimethyloxazolone-5 obtained in pure form at a boiling point of 63 - 640 C.

Example 2: A melt stabilized with 0.5 β hydroquinone 60 g of N-methacryloyl-a-aminoisobutyric acid (melting point 160-1620 C) is within of 30 minutes at 2600 C under normal pressure in the apparatus described in Example 1 implemented. 2-Isopropenyl-4,4-dimethyloxazolon-5 is from the reaction mixture with Petroleum ether extracted and then distilled in vacuo (boiling point 45 - 460 c / o, 6 torr).

Example 3: Gives through the reaction tube described in Example 1 within 45 minutes at 2800 C a solution of 40 g of N-methacryloyl-1-aminocyclohexanecarboxylic acid in 50 ml of dimethylformamide. The dimethylformamide is distilled off from the reaction mixture and then the distillation residue to separate the unreacted starting product of the educated Oxazolone added to petroleum ether. After evaporation of petroleum ether and crystallization of the residue from ethyl acetate give 2-isopropenyl-4,4-pentamethyleneoxazolone-5 (Melting point 53-540 C).

Example 4 Analogously to Example 1, 60 g of N-acryloylaminoisobutyric acid are used (Melting point 186-1870 c), stabilized with 0.5% hydroquinone, at 2600 C / 14 Torr implemented. The reaction mixture becomes 2-vinyl-4,4-dimethyloxazolone-5 with Petroleum ether extracted and then by vacuum distillation (boiling point 26 - 280 C - 0.5 Torr).

Example 5: 60 g of N-methacryloyl-α-aminoisobutyric acid stabilized with 0.5% hydroquinone is allowed to melt over the tube walls heated to 2600 ° C. within 30 minutes of a thin film evaporator. The reaction product becomes after condensation worked up in a cooler connected downstream of the thin-film evaporator as in Example 2.

Example 6s 10 g of N-methacryloyl-a-aminoisobutyric acid, dissolved in 50 ml of diethylene glycol dibutyl ether are at 2500 C and 12 Torr in the example 1 described apparatus dehydrated.

The 2-isopropenyl-4, 4-dimethyl-oxazolon-5 formed is by vacuum distillation isolated.

Example 7: In 50 ml of an isomer mixture of triaryldimethanes (Marlotherm S, Chemische Werke Hüls) 10 g of N-methacryloyl-α-aminoisobutyric acid are dissolved and C, 05 g hydroquinone.

This solution is under a moderate stream of nitrogen at 100 torr heated to 2500 C. The condensate occurring in a separator is according to the example 2 elaborated; Example 8t In one with a heatable dropping funnel, stirrer and distillation attachment The 1 l three-necked flask is provided with 250 ml of paraffin oil and heated to 2500 ° C. while stirring. At a pressure of 70-100 Torr, 60 g at 0.5 are left in the course of 30 minutes % Hydroquinone was added to N-methacryloyl-α-aminoisobutyric acid melted in the dropping funnel drip.

The 2-isopropenyl-4,4-dimethyl-oxazolon-5 formed is via a Distillation attachment removed.

Claims (1)

Process for the preparation of substituted oxazolones of the general formula from acylaminocarboxylic acids or esters of the formula where in both formulas R1 and R2 denote lower alkyl radicals or, taken together with the adjacent G atom, form a carbocyclic ring, R is an alkyl or alkenyl radical and R is hydrogen or a lower alkyl radical, characterized in that the acylaminocarboxylic acids or esters in pure distribution or be heated in a thin layer to temperatures above 2000 C.