Methyl ricinoleate is converted in 57% yield into methyl (E)-12-oxo-Umwandlung ungeslttigter Fettsluren -Nukleophile Additionen 10-octadecenoate (4) by oxidation of the 12-OH group and conjugaan (E)-l2-0xo-1O-octadecensauremethylester. Ricinolsauremetion of the double bond. The enone fatty acid methylester 4 reacts in thylester wird durch Oxidation der Hydroxylgruppe und Konjugation high yield with anions of 1,3-dicarbonyl compounds, nitroalkanes, der Doppelbindung mit 57% Ausbeute in (E)-12-0xo-10-octadecenacylanions from aromatic aldehydes and cyanide to new C10-funcsauremethylester (4) uberfuhrt. An den Enonfettsauremethylester 4 tionalized fatty acids. The nitroalkyl adducts can be converted into werden anionisierte 1,3-Dicarbonylverbindungen, Nitroaliphate, pyrroloid and furanoid fatty acids. Acylanionen aus aromatischen Aldehyden und das Cyanidanion zu neuen C10-funktionalisierten Fettsauren in hohen Ausbeuten addiert. Die Nitroalkyladdukte lassen sich in Pyrrol-und Furanfettsauren umwandeln.
The enolates of fatty acid methyl esters la-g are dimerized in good yields (56 to 73%) by means of oxidative coupling with copper(I1) bromide to dialkylated succinic esters 2a-g. The configuration of meso-la was established by independent synthesis. On treatment with ozone the unsaturated dimer 2c is converted to the tetracarboxyl compound 6. Epoxidation of 2g leads to the corresponding bisepoxy diester 7.Renewable raw materials, as fatty acids or carbohydrates, are gaining increasing interest as industrial feed stockL2]. Reasons are a good biological disintegration, unlimited supply, and a more neutral carbon dioxide balance as compared to mineral oil as feed stock.Whilst the chemistry of the carboxyl group of fatty acids is much advanced in laboratory and on a technical scale [2b], the chemistry at the C H bonds and the double bond of fatty acids is far lessIn this paper we report on the oxidative coupling of the enolates of fatty acid esters 1 to 2,3-dialkylsuccinic diesters 2. Some of the succinic acid derivatives have already been synthesized by alkylation and subsequent dimerization of malonic estersL31 or by coupling of a-bromo estersL4I. The photodimerization of the methyl alkanoates gives only poor yields151. The oxidative dimerization of short-chain ester enolates has been achieved with 12L6] or CuBr2 ['] as oxidants and by way of electrochemical For unbranched alkanoates copper(I1) salts appear to be the reagents of choice. Methyl succinates have also been prepared by Kolbe electrolysis of the corresponding methyl malonates[8bl.For the preparation of the succinates 2a-g the methyl esters l a -g in T H F are added slowly to 1 equiv. of LDA in T H F at -78°C. After 15 min 0.9 equiv. of dry copper(I1) bromide is added all at once with rapid stirring. During an additional 30 min the color of the solution turns to brown. The reaction is quenched by the addition of water at -78°C followed by an acidic workup procedure and purification by distillation (eq. 1).At -78°C the Claisen condensation of the esters, which competes with the oxidative dimerization, is suppressed to an extent of 4 to 8%, but the lithiation of saturated fatty acid esters with chain lengths >CI4 becomes difficult because of their low solubility at that temperature. However, this effect can be compensated by the addition of 10 vol-% Z , Z -C~H~~-C H = C H -C H~-C H = C H -( C H~) S - 56(66)[ a ] Yields i n parenthesis a r e colculoted on converted 1.HMPTf91, which apparently increases the rate of lithiation. With regard to the solubility under the conditions of lithiation, methyl oleate (lg) and methyl linoleate (If) behave like methyl decanoate (lb), possibly due to the effect of the Zdouble bonds.Rathke"] proposed radicals as intermediates in the coupling reaction. In order to prevent these from undergoing further oxidation to cations by copper(I1) only 0.9 equiv. of copper(I1) bromide is added. Thus, the side products, abromo esters, resulting from the oxidation, are formed to an extent of only 6 to 10%. For the same reason a high enol...
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