One-step synthesis of a fluorescein derivative and mechanistic studies

We report a convenient method for the one-step synthesis of a fluorescein derivative under acidic conditions. Mechanistic studies indicate that the acid-promoted condensation of o-tolualdehyde and 4-chlororesorcinol to form the fluorescein derivative proceeds through a cyclization-oxidation pathway while an alternative oxidation-cyclization pathway remains possible. (c) 2012 Elsevier Ltd. All rights reserved.