Synthesis of 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl

Stable free radicals are critical and can be used as spin probes as well as potential application as molecular devices and switches. Verdazyls are stable radicals with a large potential for structural diversity. We are investigating the chemistry of verdazyl free radicals so that we can better understand how they may be covalently incorporated into other structures so that applications, such as spin probes, may be realized.  Here we report the synthesis of 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl. 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl free radical was synthesized with 1 mmol of 2,4-Diisopropylcarbonobishhydrazide dihydrochloride and 2eq of NaOAc dissolved in minimal amounts of ethanol.  The solution was added & allowed to stand at room temperature for 24h.  Minimal amounts of toluene were added to the solution mixture with 1.5eq of Benzoquinone. Condensations with aldehydes tend to form tetrazanes and finally oxidation to give the free radicals. The introduction of isopropyl groups results in free radicals that show greater solubility in a variety of solvents and are more stable than their methyl substituted counterparts.  GCMS and ¹H-NMR preliminary measurements confirmed the identity of the 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl radical with diastereotopic identities.  What makes the 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl radical unique is the 3-hydroxymethyl group.  What we want to do with the 3-hydroxymethyl group is oxidize it to become an aldehyde and its conversion to a leaving group.  Further research studies will conduct the oxidation of 1,5-Diisopropyl-3-hydroxymethyl-6-oxo-verdazyl via MnO₂.  An alternative to the oxidation reaction would be an extensive Mitsunobu reaction to convert the 1° alcohol of the verdazyl radical to an ether.