Identification of sodium cromoglicate by colour reactions

Chromone-2-carboxylic acid (3) reacts with aminopyrazolone (2) in methanoli c hydrochloric acid to yield the orange-red polymethine dye 4. Treating dim ethyl cromoglicate (6) with compound 2 and perchloric acid leads to the tet raperchlorate 7 of the red azamerocyanine 8. The phenol 9, obtained from al kaline hydrolysis of sodium cromoglicate (1a), couples with diazotized sulf anilic acid to form the red azo dye 10. The chromone 6 condenses with 1,3-d imethylbarbituric acid (DMBA) in acetic anhydride/acetic acid to the red ox onole 12. Cromoglicinic acid (1b) reacts under these conditions to yield th e yellow polymethine dye 14, whose structure is elucidated by X-ray analysi s.