General procedure for the synthesis of 5-chloro[1,6]diazanaphthalene from 1,6-naphthopyridin-5(6H)-one: the product of Example 36d (0.250 g, 1.71 mmol) was mixed with phosphorus trichloride (4 mL) and reacted under nitrogen protection at 80 °C for 18.5 hours. Upon completion of the reaction, the volatiles were removed by vacuum distillation. The residue was slurried with ice water and adjusted to pH 7-8 with concentrated ammonium hydroxide solution.5-Chloro[1,6]diazanaphthalene was collected by vacuum filtration, washed with water and dried under vacuum to give a gray solid (0.245 g, 87% yield) of sufficient purity to be used in subsequent separations.
