Weinreb amides are useful in reducing acid chlorides (and esters) to form ketones due to the fact that the more reactive keto group is unmasked only after treatment with acid and water, which destroys the reducing agent. One example I have been given of use of Weinreb amides is the following:

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We see here that the 1,3 dicarbonyl compound is formed. This implies that under these conditions, the ester lithium enolate does not attack the ester moiety in the Weinreb intermediate, presumably because it is not reactive enough. Is this a general case? If the ester was, say, replaced by a ketone, would we still form the 1,3 diketone species or would we have attack of this carbonyl centre to form an alcohol?

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    $\begingroup$ I think the steric effect of the tBu group is important in blocking possible enolate attack on the ester. Does this reaction work for methyl or ethyl ester enolates? $\endgroup$ – Waylander Mar 21 '19 at 11:00
  • $\begingroup$ I don't really understand why this is better than just running a Claisen condensation. The $\beta$-keto ester product will tautomerize after the reaction, which it likes does here as well. Then it's no really prone to reacting again. $\endgroup$ – Zhe Mar 21 '19 at 12:05

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