Method for preparing chloromethyl pyridine derivative by electrochemical selective dechloridation

Abstract

The invention discloses a method for preparing a chloromethyl pyridine derivative by electrochemical selective dechloridation. The method comprises the following steps: taking an acidic solution as a reaction medium, and adding a trichloromethyl pyridine derivative as shown in formula (I) into the acidic solution to obtain an electrolytic reaction solution; carrying out electrolytic reaction in an electrolytic cell which takes a carbon material as a cathode and takes a chemical inert conductive material or a titanium metal material coated with a noble metal oxide as an anode at a temperature being 20-40 DEG C, wherein the current density is 0.5-10A / dm<2>, and the pH is equal to 1-6; and after the electrolytic reaction is ended, separating and purifying to obtain the chloromethyl pyridine derivative as shown in formula (II). The method realizes carrying out hydrogenation reduction on the trichloromethyl pyridine derivative with relatively high chemical selection (greater than or equal to 75%) and a relatively high yield (greater than or equal to 70%) to obtain the chloromethyl pyridine derivative, so that mercury and zinc powder with high toxicity are avoided, constant-current electrolysis is realized, and electrolytic potential is not needed to be controlled, and therefore, the method is beneficial for industrial production.

Description

(1) Technical field [0001] The invention relates to an electrochemical selective dechlorination method for trichloromethylpyridine derivatives, in particular to a method for preparing chloromethylpyridine derivatives by electrochemically selectively hydrogenating chlorine substituents on the methyl groups of trichloromethylpyridine derivatives . (2) Background technology [0002] Chloromethylpyridine derivatives as shown in formula (II) are very important pesticides or pharmaceutical intermediates, such as 2-chloro-5-chloromethylpyridine is highly efficient, low-toxic, Key intermediates for low-residue new pesticides. [0003] [0004] In formula (I), X is H, F, CN, NR 2 Or OR, wherein R is H, C1~C6 alkyl, benzene ring, fluorobenzene ring or chlorobenzene ring, n is 0 or 1; m is 0, 1, 2, 3 or 4; X in formula (II) , m and n are the same as formula (I). [0005] The preparation of chloromethylpyridine derivatives as shown in formula (II) by the chlorination method has t...

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Problems solved by technology

[0008] The purpose of the present invention is to provide a method for preparing chloromethylpyridine derivatives by electrochemical selective dechlorination, using carbon materials such as graphite and activated carbon as cathodes, and using solvents such as water, C1~C4 alcohols, acetonitrile and benzenesulfonic acid Various trichloromethylpyridine derivatives as shown in formula (I) are carried out electrolysis experiment in the acidic solution that supporting electrolytes such as sodium, lithium chloride form, by controlling the pH=1~6 of above-mentioned electrolytic reaction solution, various Trichloromethylpyridine derivatives can be selectively reduced to chloromethylpyridine derivatives as shown in formula (II), and the present invention solves the side effects of trichloromethylpyridine derivatives as shown in formula (I) The problem of "low utilization rate of zinc powder and the production of a large amount of high-COD zinc chloride-containing wastewater that is difficult to recycle" in the existing recycling technology and the "high use of trichloromethylpyridine derivatives" in the existing electrochemical hydrogenation dechlorination technology Toxic metallic mercury", "difficult product extraction" and "low selectivity of hydrodechlorination"

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