Ibudros,Manetti-Roberts,Italy,1978
In a 1,000 ml three-necked flask equipped with a stirrer, a dropping funnel
and a silica gel guard pipe, 46.7 g hydroxylamine hydrochloride are dissolved
cold in 480 ml methanol. Separately a solution of 56.1 g KOH in 280 ml
methanol is prepared, heated to 30°C and admixed, dropwise under stirring to
the hydroxylamine solution. All successive temperature increases during this
admixture are prevented by cooling in an ice bath. After the whole KOH
solution has been admixed, the mixture is left standing for 5 minutes so as to
attain the complete precipitation of the KCl.
Separately, 72.02 g ethyl 2-(4-isobutylphenyl)-propionate, obtained by the
esterification of 2-(4-isobutylphenyl)-propionic acid with ethanol and
concentrated H2SO4, are solved with 100 ml methanol, this solution is
introduced drop by drop into the reaction flask, and stirred and cooled for 5 hours on an ice bath. Thereafter it is suction filtered, the residue is washed
with all together 50 ml methanol, the wash is added to the filtrate, thereafter
the whole is evaporated in a water bath with a rotating evaporator at a
reduced pressure, until 100-200 ml of a concentrated solution are obtained.
This solution is poured into a 200 ml beaker into which are stirred
approximately 1,000 ml 1.25N acetic acid. This mixture is left standing for 24
hours, thereafter suction filtered. The resulting filtrate is taken up with 100 ml
petroleum ether at 40°C to 60°C, in order to solve any possible residue of
unreacted starting ester, and refiltered. Approximately 50g of 2-(4-
isobutylphenyl)-propiohydroxamic acid are obtained, having a melting point of
119°C to 121°C on Kofler's hot stage.
