(2) Synthesis of 2-chloro-1,5-diazanaphthalene. A 50 mL round bottom flask was charged with 1,5-diazanaphthalene N-oxide (98 mg, 1.355 mmol) and phosphorochloride (2 mL, 21.457 mmol). The reaction mixture was placed in an oil bath at 100 °C and the reaction was stirred for 8 hours. After completion of the reaction, the solvent was removed by rotary evaporator under reduced pressure. The residue was neutralized with saturated NaHCO3 solution (2 mL) and extracted with ethyl acetate (2 x 20 mL). The organic phases were combined, washed with saturated NaCl solution (2 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with 60% ethyl acetate/hexane as eluent to afford 2-chloro-1,5-diazanaphthalene (78 mg, 35% yield). Mass spectrum (ESI positive ion mode) m/z: calculated value C8H5ClN2 [M+H]+ 165.0, measured value 165.0. 1H NMR (300 MHz, CDCl3) δ ppm: 7.64 (d, J=8.77 Hz, 1H), 7.66-7.72 (m, J=4.38 Hz, 1H), 8.35 (t, J=8.77 Hz, 2H), 8.99 (dd, J=4.17,1.68Hz, 1H). 4-Chloro-1,5-diazaphthalene (86 mg, 39% yield) was also isolated. Mass spectrum (ESI positive ion mode) m/z: calculated value C8H5ClN2 [M+H]+ 165.0, measured value 165.0. 1H NMR (300 MHz, CDCl3) δ ppm: 7.75 (dd, J=8.55,4.17Hz, 1H), 7.79 (d, J=4.68Hz, 1H), 8.47 (dd, J=8.62,1.68Hz, 1H), 8.47 (dd, J=8.62,1.62Hz, 1.68Hz, 1H). 8.62,1.61Hz, 1H), 8.87 (d, J=4.68Hz, 1H), 9.11 (dd, J=4.09,1.61Hz, 1H).
