Metal- and Acid-Free C–H Formylation of Nitrogen Heterocycles: Using Trioxane as an Aldehyde Equivalent Enabled by an Organic-Soluble Oxidant

A metal-free, innate, and practical C–H formylation of nitrogen heterocycles using trioxane as a formyl equivalent is reported. This reaction provides a mild and robust method for modifying medicinally relevant heterocycles with an aldehyde handle. The use of an organic soluble oxidant, tetrabutylammonium persulfate, is critical in promoting the desired coupling.