Methylhydrazine → 3,5-Dibromoisonicotinaldehyde methylhydrazone

Temperatur

100 °C

In analogy to GP 1, 2.15 g of 3,5-dibromo-pyridine-4-carbaldehyde (8.12 mmol, 1 eq; commercially available or prepared as described in U.S. Pat. No. 6,232,320 or WO2005110410) were dissolved in 36 mL 1-propyl alkohol, treated with 0.65 mL N-methyl hydrazine (12.17 mmol, 1.5 eq.) and heated to 100° C. for 30 min (employing a Biotage Initiator® microwave oven in batch mode). The reaction mixture was concentrated, the residue partitioned between water and ethyl acetate, the aqueous layer reextracted with ethyl acetate, the combined organic layers dried and concentrated in vacuo to yield 2.29 g of the desired product (7.82 mmol, 96% yield), which was used in the subsequent cyclization without further purification steps.