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Oxalic acid to malonic acid

The reagents I have used here are $\ce{LiAlH_4}$ which reduces the carboxylic groups into alcohol.Used $\ce{HIO_4}$ which breaks up the molecule into methanal. Then I applied Grignard reagent which consisted ethyl for the alkyl part.Then I tried to oxide the terminal carbon into $\ce{COOH}$ but could not find a suitable reagent.

What is a better approach and a method to solve this question.

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    $\begingroup$ Arndt–Eistert, maybe? $\endgroup$ Aug 20 '18 at 9:02
  • $\begingroup$ en.wikipedia.org/wiki/Arndt%E2%80%93Eistert_reaction $\endgroup$
    – Soumik Das
    Aug 20 '18 at 10:53
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    $\begingroup$ I would be wary of using a multistep reaction to try to homologate only one carboxylic acid group of oxalic acid... maybe forming a monoester first would work. $\endgroup$
    – orthocresol
    Aug 20 '18 at 12:35
  • $\begingroup$ I would fully reduce to the diol and convert to the epoxide. Then, form the halohydrin and oxidize to $\alpha$-chloro acetic acid. Should be pretty straightforward after that. Going through the halohydrin would allow you to desymmetrize the starting material. $\endgroup$
    – Zhe
    Aug 20 '18 at 14:01
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The Arndt-Eistert procedure suggested above seems very applicable to this problem. To use it we need ethyl oxalyl chloride. This can be prepared in 2 steps from oxalic acid by first esterification to form diethyl oxalate procedure here then reaction with PCl5 to form ethyl oxalyl chloride procedure here. This can undergo the Arndt-Eistert mechanism here with excess diazomethane then either irradiation or treatment with silver oxide to give monoethyl malonate. Simple base hydrolysis then gives the required.

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Assuming you want oxalic acid as the only source of carbon

$\ce{(COOH)2 ->[\Delta, -CO2] CO ->[Cl2] COCl2 }$

$\ce{(COOH)2 ->[LiAlH4; H3O+] (CH2OH)2 ->[H3O+,\Delta] CH3CHO }$

$\ce{CH3CHO ->[B:-] CHO-CH2- ->[COCl2, huge excess; H3O+] CHO-CH2-COOH ->[Ag2O] CH2(COOH)2 }$

The key here is to split target molecule into $\ce{C1}$ and $\ce{C2}$ fragments and then find a way to find a way to make enolizable $\ce{C2}$ compound from oxalic acid. There is more then one way to obtain phosgene, one I pointed here wouldn't work in a lab. AFAIK phosgene can be obtained by thermal decomposition of oxalyl chloride, but I couldn't find trustworthy looking reference with quick googling.

rearrangement of ethylene glycol might required rather harsh conditions.

..... That one was fun.

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    $\begingroup$ By Arndt–Eistert any luck? $\endgroup$
    – Pole_Star
    Aug 21 '18 at 12:42
  • $\begingroup$ @starunique2016 The common restriction in this type of problems is either to not use outer sources of carbon or not use other organic compounds. Besides, Arnds-Eistert isn't very common. For this reasons I do not consider Arnds-Eistert a valid step for this problem unless OP states otherwise by quoting exact wording of the problem. $\endgroup$
    – permeakra
    Aug 21 '18 at 21:02
  • $\begingroup$ If i want by Arndt-Eistert only? $\endgroup$
    – user57048
    Aug 22 '18 at 10:15
  • $\begingroup$ That ethylene glycol one i have my doubts $\endgroup$
    – user57048
    Aug 22 '18 at 10:16
  • $\begingroup$ @user57048 Rearrangement or synthesis ? Rearrangement is referenced in literature, it is a variant of pinacol–pinacolone rearrangement. $\endgroup$
    – permeakra
    Aug 22 '18 at 11:11

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