Synthesis of Bromovinylhydrazine Diester Precursor

Example 4

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2,2′-(1,2-Bis((E)-3-bromoacryloyl)hydrazine-1,2-diyl)diacetic acid (210 mg, 0.509 mmol) in dichloroethane (15 ml) was added (COCl)₂ (505 mg, 4.01 mmol), followed by addition of 0.040 ml of DMF. After stirred at RT for 2 h, the mixture was concentrated and co-evaporated with dichloroethane (2×20 ml) and toluene (2×15 ml) to dryness to afford the title crude product (which is not stable) for the next step without further purification (245 mg, 107% yield). MS ESI m/z calcd for C10H₉Br₂Cl₂N₂O₄ [M+H]⁺ 448.82, 450.82, 452.82, 454.82, found 448.60, 450.60, 452.60, 454.60.