A one-pot synthesis and X-ray crystallographic and computational analyses of methyl-2,4-dimethoxysalicylate - a potential anti-tumour agent

The thermal decarboxylation of 2-methoxycarbonyl-5-(4’-nitrophen-oxy)tetrazole (1a) with the electron-rich, aromatic compounds (anisole, N,N-dimethylaniline, 1,4-dimethoxybenzene, and 1,3,5-trimethoxybenzene), neat or in polar solvents (DMSO, DMF, and CH3CN), is investigated. The solid phase thermal decomposition of a mixture of 1a, 1,3,5-trimethoxybenzene, and a Lewis acid (AlCl3) produces methyl-2,4-dimethoxysalicylate (8) in good yield, instead of the expected 2,4,6-trimethoxybenzoic acid. The X-ray structure of 8 shows intramolecular hydrogen bonds between the carbonyl oxygen and hydrogens of Me and OH groups. A measured pK(a) value of 6.8 compares well with a value of 6.4 estimated using the [C=O...H...O] hydrogen bond distances.