Preparation,H-1 and C-13 NMR, and ab initio/IGLO study of mono-O-protonated deltic acid and theoretical investigation of di-, tri-, and tetra-O-protonated deltic acids

The hitherto elusive mono-O-protonated deltic acid C3O3H3+ was prepared by protolysis of di-tert-butoxy deltate in FSO3H-SO2ClF and in FSO3H:SbF5 (Mag ic Acid; 1:1 molar solution) in SO2ClF as solvent at -78 degrees C and was characterized by H-1 and C-13 NMR spectroscopy. The structure and NMR chemi cal shifts were also calculated by the ab initio/IGLO method. No NMR eviden ce was found for persistent di-O-protonated deltic acid under these conditi ons, although a limited equilibrium with the mono-O-protonated species can be involved. Di-, tri-, and tetra-O-protonated deltic acids were also studi ed by ab initio/IGLO method.