Boron trifluoride → Z-3-(3-Pyridinylmethyl)imino-10beta-piran-2-OL

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Reaction Steps

To a stirring solution of (−)-2-hydroxy-3-pinanone (10.00 g, 59.4 mmol) in benzene (500 mL) was added 3-pyridylmethylamine (6.66 mL, 65.4 mmol) in one portion. Boron trifluoride diethyletherate (0.7 mL, 5.9 mmol) was added in one portion and the reaction was refluxed under N2 for 5 h, then stirred at room temperature for an additional 16 h. The benzene was removed by rotary evaporation and the resulting residue was stirred in saturated NaHCO3 solution (100 mL) for 1 h. This was then extracted with chloroform (3×100 mL), and the combined extracts dried (Na2SO4), filtered and concentrated by rotary evaporation. The resulting dark brown oil was purified by column chromatography, using a chloroform:methanol gradient (5:1 to 1:1, v/v) as eluent. The light yellow oil was crystallized by dissolving in hot ethyl acetate (50 mL) and placed in a freezer at −4° C. for 16 h. After warming to room temperature, the crystals were filtered, washed with ice-cold ethyl acetate, and dried on a hi-vacuum pump to yield off-white crystals (8.04 g, 52.4% yield).

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