Photo-Induced N–N Coupling of <i>o</i>‑Nitrobenzyl Alcohols and Indolines To Give <i>N</i>‑Aryl-1-amino Indoles

A novel method to synthesize N-aryl-1-amino indoles was established by the photoinduced N–N coupling reaction. This protocol is by treatment of o-nitrobenzyl alcohols and indolines in the presence of TEAI and acetic acid with a 24 W ultraviolet (UV) light-emitting diode (LED) (385–405 nm) irradiation. The products bearing an aldehyde group can be further transformed to fluorescent probes based on Rhodamine 6G derivative 11, which shows a high specificity and sensitivity for Fe3+.