CS232342B1 - Processing of 3-alylrhodanine - Google Patents

Description

The invention relates to a process for preparing 3-allylrhodanine of the formula

0 = C = S \

CH ₂ CH = CH ₂ used as an important semi -over in the production of photographic sensitizers. The substance is prepared by long - term boiling of elyl isothiocyanate with thioglycolic acid in an aqueous alcoholic medium and finally distilled under vacuum (eg ANDREASCH, ZIPSERs Honatsh. 24.

504j BUTCHCHS: Monateh. 32, 12). The most serious problem in this preparation is the preparation and isolation of the elylisothiocyanate, which is highly toxic and has a strong odor. Even the final isolation of the product by shaking from the reaction mixture with solvents, predominantly diethyl ether and subsequent distillation under vacuum is not too suitable for the preparation of larger amounts and is usually rather lossy. ,

It has now been found that the above-mentioned 3-allylrhodanine can be prepared without major problems by minimizing odor and toxic effects by believing a mixture of allyl chloride or allyl bromide with equivalent or up to 10% reduced potassium, sodium or sodium thiocyanate ammonium in aqueous-alcoholic medium. The allyl isothiocyanate 3e formed in the reaction mixture does not isolate, but after addition of an equivalent or up to 50% increased amount of thioglycolic acid, the reaction mixture is further boiled until the formation of the

3-allylrhodanine. After concentrating the reaction mixture by distilling off a portion of the liquid, the residue is cooled until the product crystallizes. After being sucked off and washed with ice water, it is finally washed with a mixture of equal portions of petrol and ethanol and finally 100% petrol. This removes residual starting materials. After drying in air, a pure product is obtained having a melting point of up to 46 DEG C. in a relatively high yield

In the PM process according to the invention, the isolation of allylieathiocyanate is eliminated, it operates in one and a low-volume apparatus with sieve ee pure product without otherwise necessary vacuum distillation.

i ¹ k k 1 ai

180 parts by weight of potassium thiocyanatene and 200 parts by volume of allyl bromide are heated to reflux until thiocyanatene has disappeared. 120 parts by weight of 88% thioglycolic acid of 50 parts by volume of water are then added and the mixture is refluxed for 30 to 50 hours until the reaction is complete. Finally, 110 volumes of liquid are distilled off. The residue in the flask was cooled in an ice bath until the oily product initially solidified with a crystalline mass. It sucks off and suffocates thoroughly. Wash the cake with ice water and bake in portions with 100 parts by volume of a mixture of equal parts of ethanol and petrol. Do not bite the cake with gasoline and air dry. 112 parts by weight of Klet product are obtained having a melting point of 45-46 ° C, i.e. 64.6% of theory. «

The same results are obtained using equivalent amounts of allyl chloride, sodium ammonium thiocyanate 81.

Claims (1)

SUBJECT OF THE INVENTION A process for preparing 3-allylrhodanine of formula CH, - S I ² I O = C OS! CHgCHsCHg characterized by boiling a mixture of allylchloride slylhromide with an equivalent or even a 10% reduction in potassium, sodium or ammonium thiocyanenene in aqueous ethanol until the reaction is complete, adding an equivalent or 50% increased amount of thioglycolic acid, Boiling until completion of the reaction, the product is isolated by concentrating the reaction mixture, precipitating the product by cooling to crystallization, aspirating, washing with ice water, a mixture of gasoline with ethanoles and finally gasoline.