Separation and preparative isolation of phenolic dialdehydes by on-line overpressured layer chromatography

The Reimer-Tiemann reaction carried out in a heterogeneous solid-liquid medium was found to give the isomeric dialdehydes 2-hydroxy-1,3-benzenedicarboxaldehyde and 4-hydroxy-1,3-benzenedicarboxaldehyde. The PRISMA model was employed to optimize the eluent mixture, and with careful choice of silica gel high-performance thin-layer chromatographic plates, the two isomers could be isolated and purified by on-line overpressured layer chromatography.