The reaction of 2,3-dimethylaniline (I) with chloral hydrate (II) and hydroxylamine in hot aq. HCl gives the isonitrosoacetanilide (III), which is cyclized by means of hot Ms-OH or H2SO4 to yield 6,7-dimethylisatin (IV). The hydrolysis of (IV) by means of KOH and H2O2 in water affords 2-amino-3,4-dimethylbenzoic acid (V), which is diazotized with NaNO2 and H2SO4 and treated with KI to provide 2-iodo-3,4-dimethylbenzoic acid (VI). The condensation of (VI) with the sodium salt of 2-(2-hydroxyphenyl)acetic acid (VII) by means of tris[2-(2-methoxyethoxy)ethyl]amine (TDA) and CuCl in DMSO gives the precursor (VIII), which is finally cyclized by means of hot conc. aq. H2SO4 to furnish the target xanthene derivative.