4-Hydroxybenzaldehyde → 5-[2-(p-Hydroxyphenyl)ethen-1-yl]imidazo[1,5-a]pyridine

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Reaction Steps

Imidazo[1,5-a]pyridine-5-methyltriphenylphosphonium chloride (4.29 g), which is prepared from equimolar quantities of triphenylphosphine and 5-chloromethylimidazo[1,5-a]pyridine, is added to slurry of sodium hydride (0.5 g, 50% mineral oil dispersion) in 100 ml of dry tetrahydrofuran at 0° under nitrogen. After 1 hour at 0° a solution of p-hydroxybenzaldehyde (0.61 g) in 15 ml of dry tetrahydrofuran is added. The reaction is allowed to warm to room temperature, is then refluxed for 1 hour, cooled and acidified with dilute sulfuric acid. The aqueous layer is washed with ethyl acetate, adjusted to pH=7 with 50% sodium hydroxide and extracted with ethyl acetate. The organic phase is dried over sodium sulfate and evaporated to yield 5-[2-(p-hydroxyphenyl)-ethen-1-yl]-imidazo[1,5-a]pyridine.

Provenance & Evidence