DE1468142B - Process for the preparation of 1 chlorine and 1,2 dichloro or 1 bromine and 1,2 dibromo cyclobutane 1,2 dicarboxylic acids or their esters or nitriles - Google Patents

Description

Halogenation products of cyclobutane-l ^ -dicarboxylic acid, like ζ. B. 1,2-dichloro or 1,2-dibromocyclobutane-l ^ -dicarboxylic acids and their derivatives have not yet been described in the literature.

In the Journal of Organic Chemistry, Vol. 27 (1962), pp. 423 and 428, a process for the preparation of 1-chloro-cyclobutanecarboxylic acid described therein consists in that cyclobutane monocarboxylic acid chloride is chlorinated with chlorine gas, the resulting chlorination product with methanol in the corresponding ester and the 1-chloro-cyclobutane monocarboxylic acid is obtained from the ester by hydrolysis. This Process running in several stages is uneconomical and therefore not of technical interest.

A one-step process for the production of 1-chloro and 1,2-dichloro or 1-bromo and l ^ -dibromocyclobutane-l ^ -dicarboxylic acids and their esters or nitriles found, which is characterized in that one cyclobutane-1,2-dicarboxylic acid or the corresponding derivatives of the same with chlorine or bromine at a moderately elevated temperature reacted and then the reaction mixture was distilled.

For example, 1,2-dichloro-cyclobutane-1,2-dinitrile can be used produce in good yield by in liquid l ^ -Dicyancyclobutane at a temperature from 90 to 100 ° C introduces a stream of chlorine and the desired from the chlorinated reaction mixture End product distilled off in vacuo.

In principle, the halogenation reaction is carried out in the liquid phase, either in the Melt or is carried out in the presence of a solvent or diluent. Using of a solvent, chloroform or carbon tetrachloride has proven particularly useful, but it is not excludes that other inert solvents can be used.

The reaction temperature is generally between about 60 and 140 ° C, preferably 90 to 100 ⁰ C.

If necessary, a slight overpressure can also be used to accelerate the reaction. which is then, for example, about 0.1 to about 5 atmospheres.

Cyclobutane-1,2-dicarboxylic acid are suitable starting materials for carrying out the process of the invention as well as their derivatives into consideration, whereby among derivatives, the esters, such as. B. methyl, Ethyl, propyl and butyl esters, or the nitriles are to be understood. These starting products can be used in the be chlorinated or brominated in the manner already described.

The course of the halogenation of the invention Starting products must be described as extremely surprising, since one next to the introduction a chlorine or bromine atom in the 1,2-position of the cyclobutane-1,2-dicarboxylic acid or its Derivatives should expect such in the 3,4-position. Another possible reaction of the halogen is the splitting of the not particularly stable one Cyclobutane ring, which however also does not occur.

The process of the invention thus enables the selective chlorination or bromination of the cyclobutane-1,2-dicarboxylic acid and their derivatives in the 1,2-position, process products being obtained which were previously unknown and are valuable starting materials for further syntheses. The received Compounds can be distilled without decomposition and are easily crystallizable compounds represent.

example 1

In 530 g of 1,2-dicyancyclobutane are added with stirring passed in at a temperature of 90 to 100 ° C within 2 hours 710 g of chlorine gas, hydrogen chloride escapes from the reaction mixture. After adding the entire amount of chlorine, the Leave the reaction mixture for a further 20 minutes at the above temperature and then im Subjected to vacuum fractional distillation. l ^ -Dichlorocyclobutane-l ^ -dinitrile boils at 99 ° C under a pressure of 3 torr. The one that melts at 68 ° C Compound was obtained in a yield of 875 g or 90% of theory.

Example 2

In 5 moles of cyclobutanedicarboxylic acid l ^ -dimethyl ester, chlorine gas is passed in with stirring at a temperature of 90 ° C. until the increase in weight of the reaction mixture corresponds to an uptake of 10 moles of chlorine. By subsequent fractional distillation of the reaction mixture in vacuo l-Chlorcyclobutandicarbonsäure-l ^ dimethyl ester and l ^ l ^ -Dichlorcyclobutandicarbonsäure-dimethyl ester were in a weight ratio of 2: 1 are obtained in 70 ° / ₀ yield. The isolated process products have the following boiling points:

l-chlorocyclobutanedicarboxylic acid l ^ -dimethyl ester boiling point 115 ° C / 5 Torr, ■
l ^ -Dichlorocyclobutanedicarboxylic acid l ^ -dimethyl ester bp 128 ° C / 3 Torr.

By adding traces of iodine in addition to phosphorus or phosphorus trichloride to the reaction mixture the weight ratio of the resulting process products in favor of 1,2-dichlorocyclobutanedicarboxylic acid 1,2-dimethyl ester shift.

Example 3

Chlorine is passed into 1 mole of 1,2-cyclobutanedicarboxylic acid with stirring at a temperature of 195 ° C. until the increase in weight of the reaction mixture corresponds to an uptake of 1 mole of chlorine. After cooling, the reaction product is recrystallized from water, 1,2-dichlorocyclobutanedicarboxylic acid -1.2 with a melting point of 251 ° C. _{being obtained in a yield of 70 ° / 0.}

Example 4

SOgCyclobutane-l ^ -dicarboxylic acid dimethyl ester heated to 100 ° C. with 200 g of bromine for 6 hours under reflux of bromine. Then it is not implemented Bromine is distilled off from the reaction mixture in vacuo. The remaining residue is made from petroleum ether recrystallized, whereby 1,2-dibromocyclobutane-1,2-dicarboxylic acid dimethyl ester with a melting point of 86 ° C is obtained in a yield of 65% of theory.

Claims (1)

Claim: Process for the preparation of 1-chloro- and 1,2-dichloro- or 1-bromo- and 1,2-dibromocyclobutane-1,2-dicarboxylic acids and their esters or nitriles, characterized in that cyclobutane-1,2-dicarboxylic acid or the corresponding Reacts derivatives of the same with chlorine or bromine at a moderately elevated temperature and then the reaction mixture is distilled.