Hey,
I’m trying to make the methylidene wittig product starting from 4-oxo-proline methyl ester.
First I tried a procedure of JOC 1992, 57, 2060-2065. They add methyltriphenylphosphonium bromide to potassium tert-butoxide at 3°C. after 15 min they add oxo-proline, reflux 3h, done. I tried it with dry THF instead of dry ether, it did not work. Tried twice
Then I tried procedure from J. Comb. Chem. 2007, 9, 143 157
Methyltriphenylphosphonium bromide (505.7 g, 1.42 mol) was placed in a 3-L round-
bottom flask, and the flask was put into an ice bath.
Potassium tert-butoxide (1.49 L of a 1.0 M solution in THF,
1.49 mol) was added to the reaction mixture, which was then
allowed to stir at 0 °C for 30 min. The reaction mixture was
warmed to room temperature and allowed to stir for 30 min,
followed by refluxing for 1 h, after which the reaction
mixture was cooled in an ice bath, and 3 (172 g, 707.8 mmol)
was added via pipet. The reaction mixture was removed from
the ice bath and brought to reflux until TLC showed the
reaction to be complete.
Did not work either. I think I am doing something wrong, but I have no idea what.
maybe the solvent is not dry enough. I just use dry solvent bottles from Aldrich. I tried different bottles and no improvement. Maybe I should distill my dry solvents first?
Maybe my starting material is not pure enough? But then I expect some yield and not nothing.
Any ideas how to get better yield?
thanks