I have a task to come up with a synthesis of the following molecule (2-azaspiro[5.5]undecan-3-one), but no starting materials have been explicitly specified:

This is my idea. I think that all the steps shown are quite reasonable.Do you have any critics/suggestion?

Proposed retrosynthesis

  • 1
    $\begingroup$ Look up quaternary carbon (en.wikipedia.org/wiki/Quaternary_carbon#Synthesis) or Spiro Compound (en.wikipedia.org/wiki/Spiro_compound#Preparation) $\endgroup$
    – Karsten
    Commented Apr 26, 2020 at 18:02
  • 2
    $\begingroup$ The aminomethylene grouping is a major signal for the retro-analysis. that just screams "I started life as a nitrile". $\endgroup$
    – Waylander
    Commented Apr 26, 2020 at 19:02
  • $\begingroup$ @Waylander: Indeed! Can hear it on this side of the pond. $\endgroup$
    – user55119
    Commented Apr 27, 2020 at 1:25
  • $\begingroup$ A quick note - although it wasn't explicitly stated, here on SE we generally expect people to show their thoughts on the question at hand, or at least engage in some way. The downvotes + question closure were almost certainly because that wasn't evident at the beginning. Your edit is just what was needed, so please keep that up with questions in future (I have reopened this one and tidied it up a little bit). Btw, please don't repost questions; just edit them and they will pop back up to the top of the front page. $\endgroup$ Commented Apr 27, 2020 at 9:30
  • $\begingroup$ I think your reaction of the hydroxy acid with HCN/KCN more likely to give you the lactone $\endgroup$
    – Waylander
    Commented Apr 27, 2020 at 9:40

1 Answer 1


I think this can be done in 2 steps though I can't find a literature example.

  1. Alkylate the anion of the commercially available cyclohexane carbonitrile (cyclohexyl cyanide) with ethyl acrylate.

  2. Hydrogenate the resulting cyano-ester over Pt to reduce the -CN to -CH2NH2 which with spontaneously cyclise to give the required product.


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