Abstract: Ten bis-pyridinium salts as antidotes for organophosphorus insecticides were synthesized. A by-product with melting point of 135℃ was obtained during the preparation of intermediate 4-(1,1-dimethylethyl) pyridine (2) and its chemical structure was proved to be 2-(4-pyridyl)-propanol-2 (5) by means of IR, NMR, MS and elemental analysis. A possible mechanism was suggested. By modifying the experimental conditions this by-product was avoided and the yield of (2) was increased from 50% to 84%.