J. Pesek, J. H. Frost
1975
Citations
1
Influential Citations
59
Citations
Journal
Tetrahedron
Abstract
Abstract Stability of thiazolidine-4-carboxylic acids and chain tautomerism are studied in acidic, basic and neutral solution. In acidic solution aliphatic substituted thiazolidine-4-carboxylic acids are stable, but aromatic substituted thiazolidine-4-carboxylic acids decompose to the mercaptal if there is not steric inhibition. Mercaptal formation establishes the presence of tautomerism because it is the only pathway through which thiol can be provided for in the reaction. It is suggested that this reaction may proceed through a sulfonium ion intermediate. In neutral solution aliphatic substituted thiazolidine-4-carboxylic acids are stable. In strongly basic solution both aromatic and aliphatic substituted thiazolidine-4-carboxylic acids decompose to the aldehyde and the aminothiol. By adjusting the base concentration, the intermediate imine is detected by α-hydrogen exchange for aliphatic systems and by line broadening or direct NMR observation of the ArCH=N proton resonance in aromatic systems.