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I understand that in E there is no electrophile the amine can attack, however, I do not understand why A is an answer as well. The amine in A can perform an intramolecular attack on the aldehyde and form the product below. Why can it not?

Also, how does the oxygen leave anyway?

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This is an example of reductive amination, which generally proceeds through two main steps: (i) condensation reaction between the amine and carbonyl to generate an imine; and (ii) reduction of the imine to the corresponding amine.

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Clearly (e) can't do this reaction since there is no carbonyl. The reason why (a) is also an answer comes down to the wording of the question - it specifically states that the product is racemic. The stereocentre in (a) is (R) in the starting material, and is not involved in the reaction so the product will exist as a single (R) enantiomer.

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  • $\begingroup$ In the question, all the amides are secondary. Secondary amines can't form imines, thus how is an imine formed? $\endgroup$ – Lat Aug 17 at 1:36
  • $\begingroup$ Fair point, they will just form iminium ions rather than imines, but the mechanism remains exactly the same. $\endgroup$ – PCK Aug 19 at 14:49
  • $\begingroup$ Ah, ok. That explains the -1 charge then in the picture. $\endgroup$ – Lat Aug 19 at 21:38

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