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Refluxing of tris-(2,6-dimethoxyphenyl)carbenium hydrogen dichloride (2b).2H2O with chloroform furnished 9-(2,6-dimethoxyphenyl) -1,8-dimethoxyxanthene (1 1 ). This cyclization process with concomitant hydride transfer to the central carbon atom is rationalized by assuming concerted breakdown of any of the intermediates (6), ( 7 ) , and (9) (Scheme 3), i.e. the operation of the intramolecular version of the disputed Olah-Svoboda mechanism of hydride transfer to triarylcarbenium ions.