Syntheses of Nitro-Substituted Aryl Diazirines. An Entry to Chromogenic Carbene Precursors for Photoaffinity Labeling

3-Phenyl-3-trifluoromethyl-diazirine derivatives with nitro and alkoxy substituents on their aromatic ring have been synthesized as carbene precursors for chromogenic detection of photolabeled products. Photolysis of the diazirines in methanol or cyclohexane gave intermolecular O-H or C-H insertion products, respectively. Spectroscopic properties of the photoproducts are such that detection of photolabeled products may be performed in a spectral region where the absorption due to most biological macromolecules is negligible. A carbon-14 analog of the diazirine was also prepared for microscale detection of labeled products. These nitro-substituted aryl diazirines should be applicable to a wide range of photoaffinity labeling studies, from tracer experiments to preparative isolation of labeled products by HPLC with spectrophotometric detection.