I was just looking at a particular synthesis method on the Organic Chemistry Portal when I saw a particularly puzzling step, involving a 1,3-dicarbonyl compound. The step which I am puzzled by is shown here:

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The second step, acid-catalysed esterification is unambiguous. It is the first step which opens the ring which concerns me. The fact that esterification occurs in the second step seems to suggest that the product of the acid-catalysed ring opening in the first step is a carboxylic acid and I simply cannot see how it can possibly form. Would someone kindly enlighten me on step 1?

  • $\begingroup$ Step 1 is probably in error and should be aq. hydroxide. Usually this cleavage is done on non-enolic beta-diketones but it can occur with enolic beta-diketones. $\endgroup$ – user55119 Feb 16 '19 at 15:51
  • $\begingroup$ This is a reverse Claisen. $\endgroup$ – Zhe Feb 16 '19 at 15:51
  • $\begingroup$ @Zhe But how do you explain the increase in the number of oxygen atoms? There is some sort of oxidation taking place right? $\endgroup$ – Tan Yong Boon Feb 17 '19 at 2:47
  • $\begingroup$ @user55119 Is it possible if you elaborate further as to what is the mechanism exactly? $\endgroup$ – Tan Yong Boon Feb 17 '19 at 2:48
  • $\begingroup$ I assume step 1 is hydrolyze the ester. Step 2 is reverse Claisen + reform ester. The reverse Claisen converts a ketone into an ester using the alcohol. Are you calling that the oxidation? $\endgroup$ – Zhe Feb 17 '19 at 13:43

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