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How do I synthesize 3-phenyloxirane-2-carbaldehyde from chloroacetonitrile?

Overall reaction scheme

My proposed route involves:

  • hydrolysis of the nitrile to form a carboxylic acid, and subsequent esterification
  • then, a Darzens reaction with benzaldehyde
  • reduction of the ester function with DIBALH and oxidation to an aldehyde with $\ce{H2CrO4}$.

Is there a better method?

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The Darzens condensation can be carried out directly from the alpha-chloronitrile. The exact reaction needed here (benzaldehyde + chloroacetonitrile) is listed 15 times in SciFinder using different base catalysts (hydroxide or an alkoxide) and conditions (sometimes with phase-transfer catalysis). The epoxide will be formed as a mixture of stereoisomers, but often chemical yields are high (reportedly upto 100%).

With the epoxide in place, the nitrile can be reduced with DIBAL to give an intermediate imine, which is converted to the aldehyde after hydrolysis. This is pretty much the same strategy you outlined, but with a couple fewer steps.

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As for sources of additional synthesis problems, old UC-Berkeley exams are usually very good. Check Chem 3A and 3B at this archive.

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