Swim tried out the reaction with triethylamine as catalyst in a methanolic medium, and used the molar eq. 1:1,1;1,1 of the subst. benzaldehyde, nitroethane, triethylamine. I will post the writeup once it has been purified, but i have some questions about the reaction conditions, which i find somewhat strange.
The patent
Patent EP960876
, says that "
The reaction could, however, also be conducted in the presence of an inert reaction solvent. Common solvents, such as aliphatic alcohols, aliphatic and aromatic hydrocarbons, and others could be utilized.". Thus the solvent of choise was methanol. IPA might have been better, because of the lower polarity.
Originally, they use the nitroethane as a solvent and reactant. They also use VERY small amounts off it, considering that the reaction temperature is sub zero temperatures. How did they go about dissolving anything in this? Swim had to use 150 mL's of methanol to get some of the 7 g's of substituted benzaldehyde into the solution at the low temperatures. And at that dilution point only about 70% went into the solution. The reaction was carried out for two hours at sub zero temperatures, and was then allowed to return to 10 degrees above freezing very slowly. At about zero degrees everything had dissolved into the soln.
So what im pondering here, is it nescassry to use such HUGE amounts of solvents here, to get everything to dissolve, or is a slurry ok, as long as some of the benzaldehyde's dissolve, which then would react and perhaps allow some more to be dissolved?
Oh well, we'll see how it goes. I'll post details on the workup and reduction later today.
Regards
Bandil