DE445524C - Process for the preparation of ªÏ-chloroacetobrenzcatechol - Google Patents

Description

Process for the preparation of tt, -chloroacetobrenzcatechol. According to the methods previously described in the literature, which go back to information from Nencki and his students (cf. Ber. D. Deutsch. Chem. Ges. 15, p. 1579, p. 29o8 [1882]; 26, RS 588 / 589 [18931; 44, p. 1548 [i9 = i], co-chloroacetobrenzcatechol is obtained by fusing pyrocatechol with chloroacetic acid and phosphorus oxychloride or of pyrocatechol with chloroacetyl chloride in a water bath by recrystallization from water, a crude product that is difficult to purify completely can be obtained in varying yields that are rarely more than 36 percent of theoretical.

It has been found that by adding an inert diluent, Benzene or toluene is particularly suitable for this purpose, and smearing is almost completely avoided can be. It was also possible to trace the course of the reaction in its individual sections to clarify exactly and to use a new method of processing. establish that it allows to work with almost no loss of raw materials.

The first product of the reaction is always O-monochloroacetate of catechol, a hitherto unknown colorless, melting at 810 and im Vacuum undecomposed volatile compound. This compound is then under the catalytic Influence of phosphorus oxychloride, which is an impurity in that of chloroacetic acid and chloroacetyl chloride represented by phosphorus trichloride is contained in the isomer C-c,) - chloroacetobrenzcatechol rearranged. However, it always forms as a by-product the O, O-dichloroacetate of catechol, producing an equivalent amount of catechol remains unchanged. Since the rearrangement of the monochloroacetate into the ketone never is done completely, it must be put together by an appropriate work-up be separated from the ketone with the other two by-products. From these Observations result in the new mode of representation explained by the following examples for the w-chloroacetobrenzcatechol, which is used as the starting material for the O-dioxyphenylethanohmethylamine (Adrenaline) is of technical importance to Example I.

== o parts of catechol are represented with 115 parts of chloroacetyl chloride ( from the acid with phosphorus trichloride) and 40o parts dry benzene on a water bath cooked. After about 24 to 36 hours the calculated amount of hydrogen chloride has been developed. For the most extensive rearrangement possible, the mixture is boiled for a few more days, then the solvent evaporated and the residue boiled with carbon tetrachloride and suction filtered while hot. The co-chloroaceto-catechol that remains on the filter is only slightly purple colored, its yield changes according to the content of the chloroacetyl chloride used of phosphorus oxychloride, but it corresponds at least to that of the previous process obtainable yields of about 40 percent of the theoretically possible. In the filtrate that separates into tetra- Chlorocarbon insoluble oil from that carbon tetrachloride that remains colorless. The 01 can either be through fractional Crystallization from benzene or by fractional distillation in vacuo (best at strong, down to 0.5 to 1 mm, reduced pressure and without interrupting the vacuum to change the templates) can be broken down into its three components. The one in benzene less soluble part that passes over first during vacuum distillation (boiling point 15 mm to 17q. °), is a mixture of catechol with its 0-monochloroacetate, which makes up the bulk. The mixture is separated by trituration with cold water, only the catechol goes into solution and is recovered. That in the air dried monochloroacetate of pyrocatechol can according to the given in Example II Way by heating with pure phosphorus oxychloride in cü-chloroacetobrenzcatechol be rearranged, so that the two main products of the reaction in the form of the desired ketones are obtained while the two by-products, catechol and its 0, 0-dichloroacetate, can be recovered in pure form.

Example II.

Pure catechol monochloroacetate, as shown in the illustration Example I is obtained as the second main product, is 5 to 1o percent of his Weight of very pure phosphorus oxychloride heated on a water bath for a few hours. It gradually solidifies crystalline even at 100 ° and changes to co-chloroacetobrenzcatechol over, which according to the manner described in Example I. is cleaned. The yield is about percent of the ester used if that Phosphorus oxychloride was completely free of tri- and pentachloride, which if necessary through Treating with ice in chloroform solution and subsequent distillation can be achieved can. A content of the named impurities causes increased dye- and smearing.

It can be seen from the two examples that the representation of chloroacetobrenzcatechins are two reactions. I. O-acetylation. II. Rearrangement by pure phosphorus oxychloride. Since the rearrangement described in Example II also takes place in benzene solution, both reactions can also be carried out in one operation unite. Care must be taken in the acetylation that the chloroacetyl chloride used is completely free of phosphorus trichloride (e.g. by using pure thionyl chloride represents) and can then after completion of the 0-acetylation by further boiling the benzene solution, with the addition of 5 to 10 percent of completely pure phosphorus oxychloride, the rearrangement cause.

Claims (1)

PATENT CLAIM: Process for the preparation of W-chloroacetobrenzcatechin from catechol and chloroacetyl chloride, characterized in that one of phosphorus tri- and pentachloride completely free chloroacetyl chloride in the presence of indifferent Solvents, such as benzene or toluene, can act on catechol and that thus formed catechol-0-monochloroacetate completely in the presence of small amounts pure phosphorus oxychloride heated to about 100 °.