Divergent Roles of Urea and Phosphoric Acid Derived Catalysts in Reactions of Diazo Compounds

Hydrogen-bond-donor catalysts enable a variety of formal insertion reactions of diazo compounds. The role of the catalyst in the reaction system may vary depending on several factors, including the nucleophilicity of the diazo compound and the acidity of the insertion partner. Ureas and phosphoric acid derivatives can offer complementary reactivity patterns when selected as catalysts for selected O–H and S–H insertion reactions of aryl- and diazo-substituted esters.