myr - 3-5-2020 at 05:16
Hello,
Recently I prepared a-methyldehydrozingerone in pretty OK yield using putative metaboric acid (made by baking boric acid and then crushing as best as
I could: it probably contains boric oxide too) as an aldol catalyst for the condensation of vanillin and butanone in glacial acetic acid.
(Sulfuric acid, btw, does not work: you instead get a strange pH sensitive oil, at first blue (!!), purple, or green which quickly decomposes to a
brown goop.)
The workup yielded a brown oil, which satisfyingly crystallized slowly into a solid mass. However, there is still a significant dark impurity.
I am attempting re crystallization with ethanol/water, but the product keeps oiling out.
Does anyone have any experience recrystallizing this product?
The end goal is a Baeyer-Villager oxidation with perborate to guaiacylacetone [1-(4-hydroxy-3-methoxyphenyl)propan-2-one]- my last attempt at making
this (without recrystallizing the aldol product) resulted in a very black tar, but with a striking, powdery-smokey odor. I'd like to see if this smell
was guaiacylacetone or instead some phenolic component of the tar.
mackolol - 4-5-2020 at 01:44
If you don't want it to oil out try something less polar, maybe toluene or hexanes, although I don't guarantee it to work.