Catalytic Mitsunobu Reaction with an Iron Catalyst and Atmospheric Oxygen

Taniguchi et al. have reported a new catalytic Mitsunobu reaction with iron(II) phthalocyanine (10 mol %) and ethyl 2-arylhydrazinecarboxylate (10 mol%) under atmospheric oxidation conditions. They describe the catalytic system in which ethyl 2-arylazocarboxylate, an oxidized azo form of ethyl 2-arylhydrazinecarboxylate, plays a role as DEAD. The azo compound-promoted Mitsunobu reactions of alcohols with carboxylic acids in the presence of triphenylphosphine successfully proceed to give ester products. Then, generated ethyl 2-arylhydrazinecarboxylate is reoxidized to its azo form by in situ iron catalyzed atmospheric oxidation.