Nitrations of 4′,5′‐dihydropsoralens: A route to radiopharmaceutical precursors

Abstract Unlike the nitration of the fully‐aromatic furocoumarin, methoxsalen, which yields a single nitration product, the nitration of the 4′,5′‐dihydro compound generates a condition‐variant mixture of three nitro products. Reduction, diazotization, and pyrrolidine‐trapping of one of these, the 4′,5′‐dihydro‐5‐nitro‐8‐ methoxypsoralen, provides a pyrrolidine triazene precursor for radioiodination of the dihydropsoralen system.