Nitrogen heterocycles, including substituted pyrrolidines and piperdines, are key compounds for the pharmaceutical industry. Recent research has achieved their synthesis through the use of hypervalent iodine, a safer, more economic and environmentally friendly oxidant. However, many of these methods rely on the use of transition metals for activation. This work sought to improve the methods by using simple inorganic Brønsted acids, where the conjugate base acts as a nucleophile and is incorporated via <i>endo</i>-type cyclization, yielding 3-piperidine and 3-pyrrolidine products. There was successful conversion of substrates using sulfuric acid and nitric acid, leading to the formation of novel heterocycles in good to excellent yields. In previous work the product formed by sulfuric acid was fully characterized and found to be a heterocyclic dimer bridged by a sulfate ester. In this work, the nitric acid reaction product has been isolated and characterized by NMR and FT-IR. The structure is also being elucidated through conventional functional group modifications.

Elucidation of novel nitrogen heterocycle

ACS Fall 2021

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