Re: GABA in GHB Synthesis



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Calcium hypochlorite: This particular reaction has received the most
attention from user

groups interested in the THF to GBL conversion. More stable that its
sodium counterpart

in solution, calcium hypochlorite converts 68% of the THF into GBL in
the presence of

acetonitrile and acetic acid when the reaction proceeds at room
temperature for up to 16

hours. Under these conditions, heating had no effect on the overall
yield of the

reaction.



Zinc dichromate trihydrate: Boasting the highest yield, this reagent
must be prepared by

the chemist due to the lack of a commercial source. The reaction is
performed at room

temperature in dichloromethane and only requires 1 hour to obtain a 70%
yield. The

reported reaction was done at room temperature leaving any effect of
temperature

variation unknown.




Zinc permanganate: Although this reagent is only cited as giving a 51%
yield, the authors

admit very little effort in attempting to optimize the reaction. Also
performed in

chloroform or dichloromethane, zinc permanganate was found to be a
superior oxidant

compared to both potassium and magnesium manganates



Peroxyphosphoric acid: Having the lowest yield of the four oxidants,
peroxyphosphoric

acid does not necessarily require the presence of a solvent. A yield of
45% was obtained

by refluxing THF in the presence of peroxyphosphoric acid for two
hours. The low yield

occurred when the THF and the oxidant were in equimolar amounts. The
authors postulate

that 2 equivalents worth of the acid could raise the yield to 80-90%.

.



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