1,8-Diazabicyclo(5.4.0)undec-7-ene → 2-(3-fluoro-phenyl)-6-methoxy-pyrazolo[1,5-b]pyridazine-3-carboxylic Acid Methyl Ester

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Reaction Steps

1,8-Diazabicyclo[5.4.0]undec-7-ene (5 ml) was added to a stirred, chilled, mixture of (3-fluoro-phenyl)-propynoic acid methyl ester (2.67 g) and 1-amino-3-methoxy-pyridazin-1-ium mesitylene sulphonate (4.89 g) in acetonitrile (80 ml) and the mixture was stirred at 0° for 1 hour then at ambient temperature for 18 hours. The mixture was concentrated in vacuo, and partitioned between ethyl acetate (150 ml) and water (150 ml). The aqueous phase was separated and further extracted with ethyl acetate (2×100 ml). The combined organic extracts were washed with water (2×50 ml), brine (25 ml), dried (MgSO4), filtered and evaporated in vacuo to give a solid which was triturated with anhydrous ether: petroleum ether (1:0.5) to give the title compound as a brown solid (2.4 g, 53%).

Provenance & Evidence