(Active Asperger Archivist)
07-16-03 07:47
No 447791
      US pat 2797243 Racemization of l-Amphetamine
(Rated as: excellent)

This patent was orginally found listed in:
Post 399065 (Worlock: "Super High Potentcy  Push/Pull  dope", Stimulants)

US Patent 2797243

Improved Method for Converting l-Amphetamine into d-l-Amphetamine

This invention relates to an improved method for obtaining greater yields of a desired optically active isomer from racemic mixtures and more particularly to a method wherein optically active isomers are converted to the corresponding optically inactive racemic mixtures.

Example 1:

A mixture of 50g of l-amphetamine and 5g of Raney nickel was charged into a Magne-Dash autoclave and the bomb pressurized with hydrogen to an initial pressure of 100lbs.  The mixture was stirred and heated at 95-100*C for 5 hours, after which time the reaction was cooled and the nickel removed by filtration. The treated base showed a rotation of 3.1*.  This would amount to about 65% racemization of the l-base present initially.

Example 2:

A mixture of 135g of l-amphetamine, 50g of Raney nickel and 1.7g of ammonia gas in 10cc of methanol was charged into Magne-Dash bomb and pressurized to 100lbs with hydrogen.  Then the mixture was heated to 150*C and maintained at this temperature with stirring for 19 hours.  The reaction was then cooled, the gases vented, and the reaction mixture filtered to remove nickel catalyst. A 50g aliquot was distilled yielding 37.4g (75%) of amphetamine; BP: 83-87*C/15mmHg, and 4.8g of residue consisting of diamine.  The rotation of the essentially d-l-amphetamine was 0.3*.

Example 3:

A mixture of 135g of l-amphetamine, 50g of Raney nickel and 0.5g of ammonia gas in 10cc of methanol, was charged into a Magne-Dash autoclave and pressurized to an initial pressure of 100lbs of hydrogen.  The reaction was heated at 150*C with stirring for 13.5 hours.  The gases were vented from the cooled reaction vessel, and the mixture filtered to remove catalyst.  A 50g aliquot sample was distilled under reduced pressure to yield 37.4g of amphetamine; BP: 83-86*C/15mmHg., and a residue of diamine weighing 10.4g.  The yield of amphetamine was 74.5%, and the rotation of essentially d-l-amphetamine was 0.2*.

Example 7:

35.5g of l-amphetamine was charged into a Magne-Dash bomb containing used Raney nickel catalyst.  This mixture was cooled in ice, and treated with a cold solution of 2.2g of ammonia gas and 10cc of methanol.  This mixture was then shaken in an atmosphere of hydrogen (initial pressure 100lbs) and at 150-155*C for 10 hours.  During this heating period a pressure of 250 lbs was developed.  The bomb was cooled, the nickel catalyst allowed to settle and the base poured out by decantation.  The solvent methanol was removed by distillation in vacuo and the residual oil fractionated.  BP: 82-86*C/15mmHg., The yield was 30g (85%) no forerun and only a small amount of still residue.  The rotation was 2.4*.

Other examples were available but at lower yields and lesser racemization.

Act quickly or not at all.
(Active Asperger Archivist)
07-16-03 08:07
No 447792
      US patent 2608583 Racemization of Amines
(Rated as: excellent)

This patent was originally referenced in:
Post 404085 (Organikum: "the distributor racemisation story", Stimulants)

US Patent 2608583

Method for Stereochemical Equilibration of Secondary Carbinamines

This patent covers the stereochemical equilibration of amphetamine and methamphetamine (most importantly)

Example 2:

30g of said racemic compound having optical rotation alphaD25 = +23.4 was heated in the presence of 10g of nickel pellets at a temperature of 160*C for 5 hours to yield, upon decantation of the reaction mixture from the catalyst and subsequent fractionation, a 1-cyclohexyl-2-methylaminopropane fraction of optical rotation alphaD25 = +13.1.

Example 3:

The d-isomer of the said compound may be racemized to a mixture of the d-l-isomers by the method below.  100g of d-amphetamine is treated with 5g of Raney nickel catalyst at 150*C for 6 hours.  The reaction is carried out in an atmosphere of nitrogen gas at 1.1 atm of pressure.  Upon decantation of the residual liquid and fractionation thereof, there is recovered almost racemic amphetamine, showing only 8% of its optical activity, in good yield.

Example 4;

Proceed as in Example 3 with, instead, the levo-isomer.  It may also be accomplished through utilization of a continuous flow system by which 1,000g of l-isomer are passed through a catalytic chamber in which is contained 100g of nickel on kieselguhr pellets maintained at a temperature of 135*C over a period of 3.5 hours at 1 atm.  Fractionation of the resulting liquid phase from this operation yielded amphetamine that retained only 12% of its original optical activity.

Example 5:

The d-isomer of methamphetamine will be racemized to the racemic mixture when 100g of methamphetamine is treated with 10g of the catalytic material comprising of nickel on kieselguhr which is maintained at 145*c for 10hours. The product maintains only 15% of its original optical activity.

Other examples were given, but have little importance or relevance here.

Act quickly or not at all.