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Diazo compounds using the Swern protocol

Posted by naturalproductman on August 13, 2012

Matthias Brewer and co-workers have reported on a nice way to make diazo compounds from hydrazones – of course diazo compounds are dangerous but that is not the point of this post.  I am kind of frustrated that maybe I failed to read carefully of their report in Organic Letters (2007, 1789), but this oxidation of hydrazones to diazo compounds using Swern conditions does not work well with aliphatic (mono alkyl or dialkyl) hydrazones – presumably because of the nucleophilic dimethyl sulfide by-product (as explained by the Kingsbury group in the supporting information in JACS, 2009, 878).

Think twice before you waste your time trying to synthesize a monoalkyl diazomethane from a hydrazone using the Swern oxidation because it likely won’t work.  Instead use Pb(OAc)4 oxidation as originally reported by Schechter in JOC 1995 4725.

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