Intramolecular Azo Coupling Reaction of Binaphthyl Compounds: Synthesis of Pyrazole-Containing Helicene-Like Molecules

A method for accessing pyrazole-containing helicene-like molecules from easily accessible NOBIN derivatives was developed. The reaction proceeded efficiently via diazonium salt intermediates, which provided a series of helicene-like molecular products in yields of 77%–89% regardless of their steric and electronic natures. The photophysical properties of the products were investigated. The 3,3′-disubstituted molecules showed a characteristic blue shift in their emission spectra. Product derivatizations were conducted, and interesting reactivities toward nucleophiles were observed.