The action of thionyl chloride on the methylene ethers of catechol derivatives. Pt. 2, Piperonyloin, piperil and hydropiperoin / by George Barger and Arthur James Ewins.

  • George Barger
Date:
[1908?]
Catalogue details

Licence: Public Domain Mark

Credit: The action of thionyl chloride on the methylene ethers of catechol derivatives. Pt. 2, Piperonyloin, piperil and hydropiperoin / by George Barger and Arthur James Ewins. Source: Wellcome Collection.

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    to 180—200°. The same carbonates are formed by treatment of the chlorine derivatives, which result from the action of phosphorus penta- chloride on the methylene ethers, with cold water, so that the effect of thionyl chloride is equivalent to that of phosphorus pentachloride and water. In the previous paper, the action of thionyl chloride on piperonyl alcohol, piperonal, and piperonylic acid was described ; in the present one, we deal with its action on compounds containing two catechol nuclei, namely, piperonyloin, piperil, and hydro- and isohydro-piperoin. A large excess of thionyl chloride was found to be necessary, and serves as solvent from which the reaction product crystallises on cooling. With smaller quantities of thionyl chloride, whether in the presence or absence of an indifferent solvent, a great deal of decomposition always took place. Besides oxidising the methylene groups to carbonyl, thionyl chloride chlorinates the fatty chain linking the two benzene nuclei. The symmetrical grouping, CH(OH)*CH(OH), of hydropiperoin is thus converted into CHC1*CHC1, but the asymmetrical grouping of piperonyloin, CH(OH)*CO, is oxidised to CCl2*CO, so that the same substance is obtained as from the diketone piperil. Under the conditions employed in the production of cyclic carbonates, thionyl chloride was found to act in an analogous way on benzoin and benzil, oxidising the former, and converting both to dichlorobenzil, in the same way that phosphorus pentachloride acts on these substances. Only in the case of the chloro-derivative from piperonyloin (and piperil) were we able to remove the chlorine from the fatty chain; we thus obtained a dicarbonate of tetrahydroxybenzil, and, from this, tetrahydroxybenzil itself; the constitution of the latter substance was proved by conversion into veratril, previously obtained from veratraldehyde. Experimental. 3:4:3': 4' -Dicarbonyldioxy-aa-dichlorodeoxybenzoin, CO<^>C6H3-CO-CCl2-C6H3<°>CO. 2-5 Grams of piperonyloin were heated with 10 c.c. of thionyl chloride in a sealed tube to 180° for seven hours. There was an unusually great pressure in the tube, and, on opening, sulphur dioxide and hydrogen chloride escaped. On cooling in a freezing mixture, the dark red solution deposited crystals, which were collected, washed with benzene, and recrystallised from xylene. Warty masses were obtained, which, after several crystallisations, separated in short, broad prisms melting at 191-—192°. The yield was 60 per cent, of:! the theoretical :
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