This one is in memoriam of my old master Prof. Dr. Hans Wynberg (Dutch Hans Wijnberg, but he liked to make it more international like with ij an y so Hans Wynberg):
(1922 – 2011) RIP Hans was role model for the film “Inglorious Bastards” he was during WW2 in the OSS, and a Jewish avenging angel spy in Nazi occupied France, OSS was the forerunner of the CIA.
Hans learned me some tricks!
Hans told me way back around 1985 already I should publish my findings on the 5,7-di(1-butoxy-3-on)-2,3-dimethylbenzofurane syntheses, because the yield was abnormally high (98% H-NMR yield, we call that quantitative). As Hans said: “This is interesting because the used reagent 2 chloro-3-butanone is almost NEOPENTYL and then still a quantitative yield! Its worth a publication!” Well it never came to that.
But today I suddenly remembered it.
Anyways here is the procedure of the synthesis:
In a solution of 35.3 grams (0.198 moles) 5,7-dihydroxy-2,3-dimethylbenzofurane and 60 milliliter (0.595 moles) 2-chloro-3-butanone in 1.5 liter acetone, 30.1 gram (0.281 moles) potassium carbonate is added. The whole solution / suspension is magnetically stirred under reflux for 5 days. In a oven dried installation sealed with calcium chloride tube. After these 5 days the acetone solute is evaporated and the residue is taken up in 500 ml water, extracted 3 times with 200 milliliter diethyl ether, the combined ether solutions were dried with 200 milliliter brine, and dried on magnesium sulfate for one night, after filtration and evaporation 61.5 grams (98%) brown oil as crude product was obtained, according to H-NMR almost pure 5,7-di(1-butoxy-3-on)-2,3-dimethylbenzofurane. After Kugelrohr distillation 40.8 grams (65%) dark sticky oil as pure product was obtained.