Good Afternoon Everyone,
I tried to hydrolyze a methyl ester yesterday (there is also a vinylsulfone present). As directed by the paper I was following (and which had worked well before in a slightly different context), I used two equivalents of LiOH and 3:2 THF/water as the solvent. After an hour I checked by TLC and the starting ester was essentially gone. I added two equivalents of HCl and extracted with ethyl acetate.
When I looked at the NMR of the product, the alkene region (approximately 5-7 ppm) seemed very busy, with all kinds of peaks that had not been present in the starting ester, although I have not yet done a detailed analysis. My tentative conclusion is that the double bond isomerized, probably both in terms of regiochemistry and stereochemistry. I was aware that alkenes could isomerize under acidic conditions, but until now I had not given much thought to basic conditions.
Obviously one thing that I can try is to use one equivalent of LiOH and to take earlier time points. For this strategy to be successful, the hydrolysis must be faster than the competing reactions. What other things should I be trying? I seem to recall that wildfyr found an interesting reference along these lines but I have forgotten the details.