The information came from the book : Secrets Of Methamphetamine Manufacture
.....One would think that the reductive alkylation of that phenylacetone derivative would yield d,l-ephedrine, and then that reduction of that
d,l-ephedrine would then give d,l-meth. That same racemic meth that results from reductive alkylation of phenylacetone. (Your Uncle prefers the buzz
produced by the racemate over the harsher, more nerve jangling buzz produced by d-meth.) Apparently, this isn't the case. The references for this
process claim that solely l-ephedrine is produced, and then reduction of this l-ephedrine, which is identical to natural ephedrine, yields that potent
but harsh d-meth.
The phenylpropanol-1-one-2 can be reductively alkylated to give l-ephedrine. Any one of several methods can be used, just as in the case of
reductively alkylating phenylacetone to meth. Method number one has to be catalytic hydrogenation using platinum catalyst.
In the example taken from US Patent 1,956,950, the chemists place 300 ml of the distilled phenyl-propanol-1-one-2 in the hydrogenation bomb along with
one gram of platinum catalyst, and 85 grams of 33% methylamine solution. They state that it's advantageous to add some ether to the hydrogenation
solution. How much is some, they don't say. They then hydrogenate the solution in the usual manner, with up to 3 atmospheres of hydrogen pressure, and
magnetic stirring of the contents of the hydrogenation bomb.
When absorption of hydrogen stops in two or three hours, the platinum catalyst is filtered out. Then the ethery hydrogenation mixture is shaken with a
volume or two of 10% HCl solution to pull the ephedrine out of the ether and into the acid water, forming the HCl salt of ephedrine. The ether layer
is separated off with a sep funnel, then the dilute acid is boiled away. The residue is diluted with a little alcohol, and then a lot more ether.
Passing dry HCl through this mixture then gives crystals of pure ephedrine hydrochloride. Their yield was around 110 grams.
My commentary on this hydrogenation? That yield is awfully low. Using phenylacetone as a guide, one should be expecting a yield around 300 grams of
ephedrine. What's up? Check out the amount of methylamine used. There are about two moles of the phenylacetone derivative, but they don't even use one
mole of methylamine. It should be the other way around, an excess of methylamine. Perhaps this is how they only get l-ephedrine from the phenylacetone
derivative. In any case, I'd much rather have 300 grams of racephedrine than 110 grams of 1-ephedrine. My thoughts are that one would be better served
just going to Chapter Eleven, and just plug in this phenylacetone derivative for the regular phenylacetone. That means two or three moles of
methylamine for each mole of phenylacetone, alcohol as solvent, and a bit more platinum catalyst in the mixture.
In the patent, they give another reductive alkylation example. They use amalgamated aluminum as the reducer, just like in Method Three in Chapter
Twelve. They take 120 grams of the undistilled fermentation product containing the 1-phenylpropanol-1-one-2, and drip it over the course of two hours
into a solution of 10 grams of methylamine in 500 ml of ether in the presence of 20 grams of activated aluminum amalgam. Simultaneously, they drip
into the mixture 20 to 30 ml of water. Stirring of the mixture is required.
The vigorous reaction that sets in is moderated by periodic cooling. When the reaction is complete after a few hours, they filter the mixture to
remove the aluminum. Then they shake the ether solution with 10% HCl solution to draw the ephedrine into the water. The ether layer is separated then
the dilute acid boiled off. The residue is thinned with a little alcohol, then dissolved in a lot more ether. Bubbling with dry HCl gives 25 to 45
grams of 1-ephedrine hydrochloride crystals.
My commentary on this procedure is identical to the last one. So little methylamine used! I haven't tried this, but I would be surprised to say the
least if more methylamine didn't greatly increase the yield of product. I would also think that any one of the activated aluminum procedures given in
Chapter Twelve could be used, just by plugging in this phenylacetone derivative for the regular phenylacetone. Also the use of ether is to be avoided
when possible. |
Safety first you know. Even is I had gallons of it and specialty fine chemicals
in my stocking, I am searching for reaction schemes that don’t use such. Certain schemes rise to the top 
no raney here and wial I can get Pt im not aiming for that. I
would like a otc from pepper and this is the best I can find for the novice. so one would expect that you would have to do an amalgum first then do
the pinacol. cool.
