Solid-phase synthesis of 2-amino-3-chloro-5- and 8-nitro-1,4-naphthoquinones: a new and general colorimetric test for resin-bound amines

Treatment of resin-bound primary or secondary alkyl and arylamines with 2,3-dichloro-5-nitro-1,4-naphthoquinone leads to the rapid formation of intensely colored (red) beads. The resulting 2-amino-3-chloro-5- and 8-nitro-1,4-naphthoquinones can be cleaved rapidly from acid-labile supports in high yields and purities. The reaction is of value as a sensitive and general qualitative test for amino groups on-resin that can be followed by cleavage for characterization and quantification of the chromogen(s) responsible for the color.