2-Chloro-3,4-dimethoxybenzaldehyde is a useful reagent in the synthesis of the human TLR4 agonist euodenine A. 2-Chloro-3,4-dimethoxybenzaldehyde is also used as a reagent in the synthesis of novel 2-methoxyacylhydrazones as potent, selective PDE10A inhibitors with activity in animal models of schizophrenia.