One-pot synthesis of N, N, N, N-tetraethyl-9H-xanthene-3,6-diamine and its conversion to pyronine B

N, N, N, N-tetraethyl-9H-xanthene-3,6-diamine (9H-xanthene) was prepared by one-pot reaction of 3-diethylaminophenol with (CH3O)3CH using pyridinium para-toluenesulfonate (PPTS) as catalyst. It was found that 9H-xanthene is photo-active and could be efficiently photo-converted to pyronine B. Treatment of 9H-xanthene with acid (HCl) produced protonated 9H-xanthene (9H-xanthene·HCl), and 9H-xanthene·HCl was spontaneously converted to pyronine B in aqueous solution. Besides, both distinct color change and turn on fluorescence were observed during the conversion. These findings not only provide a new and simple approach to the preparation of 9H-xanthene and pyronine B but also benefit the applications such as indicator and probe.

► One-pot synthesis of N, N, N, N-tetraethyl-9H-xanthene-3,6-diamine (9H-xanthene) is developed.
► 9H-xanthene is photo-active and photo-converted to pyronine B in 80% isolated yield.
► Both distinct color change and turn on fluorescence are observed during the photo-conversion.