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#76 EMM

4,5-DIMETHOXY-2-ETHOXYAMPHETAMINE


SYNTHESIS: A solution of 166 g 3,4-dimethoxybenzaldehyde in 600 mL acetic acid was well stirred, and brought up to an internal temperature of exactly 25 °C. There was added, in very small portions, a 40% solution of peracetic acid in acetic acid. The evolved heat was removed with an external ice bath, and the rate of addition was dictated by the requirement that the internal temperature should not exceed 25 °C. A total of 210 g of the 40% peracetic acid was used. The reaction mixture was poured into 3 L H2O, and the acetic acid neutralized by the addition of solid K2CO3. The neutral aqueousphase was extracted with 5x150 mL Et2O, and the solvent from the pooled extracts was removed under vacuum. To the red-colored residue there was added 300 mL 10% NaOH, and the mixture was heated for 1 h on the steam bath. This was cooled, washed once with CH2Cl2, acidified with HCl, and extracted with 5x150 mL Et2O. The pooled extracts were washed once with saturated NaHCO3 (which removed most of the color) and the removal of the solvent under vacuum gave 105 g of 3,4-dimethoxyphenol as an amber oil that slowly set up to crystals.

The above crude 3,4-dimethoxyphenol was dissolved in 200 mL EtOH, and treated with a solution of 38.1 g KOH in 300 mL hot EtOH. The clear solution of the potassium salt was a deep red color, and was promptly treated with 94.3 g allyl bromide, at a rate commensurate with the exothermic reaction. The mixture was held at reflux for 2 h. This was then added to 1 L H2O and extracted with 5x100 mL Et2O. The extracts were pooled, and removal of the solvent under vacuum gave a residue of 98 g of a black oil. This was distilled at 104-108 °C at 0.7-1.0 mm/Hg to give 59.3 g 1-allyloxy-3,4-dimethoxybenzene as a pale yellow oil with a greenish cast.

A total of 59 g of the neat 1-allyloxy-3,4-dimethoxybenzene was provided with an internal thermometer, and heated with an open flame. The color quickly became purple, then lightened to a red at 70 °C, and finally to a pale pink by 210 °C. At 240 °C an exothermic reaction set in with the temperature going up to almost 290 °C. It was held in the 270-280 °C range for several min, then allowed to return to room temperature. GC analysis showed two peaks, the second and major one being the desired 1,2,4,5-isomer. A small sample was caught by prep-GC, and it successfully seeded the crude Claissen rearrangement product. The isolated 2-allyl-4,5-dimethoxyphenol, pressed on a porous plate, had a mp of 39.5-40.5 °C which was improved to 41.5-42 °C by recrystallization from hexane.

To a solution of 9.7 g 2-allyl-4,5-dimethoxyphenol in a few mL EtOH, there was added a solution of 2.8 g KOH in 25 mL boiling EtOH followed by 5.5 g ethyl bromide. The mixture was held at reflux for 3.5 h and then poured into 200 mL H2O and extracted with 3x100 mL CH2Cl2. Pooling the extracts and removal of the solvent under vacuum gave a residue of 10.4 g of 4,5-dimethoxy-2-ethoxy-1-allylbenzene as a clear, mobile oil. It was substantially a single component by GC and was used in the following isomerization step without further purification.

A solution of 9.4 g 4,5-dimethoxy-2-ethoxy-1-allylbenzene in 10 mL EtOH was treated with 20 g flaked KOH, and heated on the steam bath. The progress of the isomerization was followed by the assay of isolates by GC. After 5 h, the reaction mixture was poured into 250 mL H2O which immediately generated a pasty solid. This was sucked free of solvent and other liquids on a sintered funnel, giving 5.5 g of trans-4,5-dimethoxy-2-ethoxy-1-propenylbenzene as an amber solid with a mp of 65-67 °C. A small analytical sample from hexane had a mp of 68 °C.

A solution of 5.0 g trans-4,5-dimethoxy-2-ethoxy-1-propenylbenzene in 27 g acetone that contained 2.2 g pyridine was magnetically stirred and cooled to 0 °C. There was then added 4.5 g tetranitromethane and, after 2 minutes stirring at this temperature, the reaction mixture was quenched with a solution of 1.5 g KOH in 26 mL H2O. The reaction mixture remained a clear deep orange color, and additional H2O was required to institute crystallization. There was the slow deposition of bright yellow crystals of 1-(4,5-dimethoxy-2-ethoxyphenyl)-2-nitro-propene which weighed, after EtOH washing and air drying to constant weight of 4.4 g. The mp was 75-76 °C.

To a gently refluxing suspension of 3.5 g LAH in 250 mL anhydrous Et2O under a He atmosphere, there was added 3.9 g 1-(4,5-dimethoxy-2-ethoxyphenyl)-2-nitropropene by allowing the condensing Et2O to drip into a shunted Soxhlet apparatus with the thimble containing the nitrostyrene. This effectively added a warm saturated solution of the nitrostyrene dropwise; the nitrostyrene was very soluble in Et2O. Refluxing was maintained for 2.5 h and the reaction continued to stir at room temperature for an additional 3.5 h. The excess hydride was destroyed by the cautious addition of 225 mL 1.5 N H2SO4. When the aqeous and Et2O layers were finally clear, they were separated, and 75 g of potassium sodium tartrate was dissolved in the aqueous fraction. Aqueous NaOH was then added until the pH was >9, and this was then extracted with 3x100 mL CH2Cl2. Evaporation of the solvent under vacuum produced 2.8 g of a clear, almost colorless oil that was dissolved in anhydrous Et2O and saturated with anhydrous HCl gas. This initially generated a solid that then oiled out. After a few minutes stirring, this began to solidify again and it finally transformed into a loose fine white solid. This was recrystallized by dissolution in 50 mL warm IPA followed by dilution with 300 mL Et2O. After a few minutes, crystals of 4,5-dimethoxy-2-ethoxyamphetamine hydrochloride (EMM) formed which were removed by filtration, Et2O washed, and air dried. These weighed 2.7 g and had a mp of 171-172 °C. Anal. (C13H22ClNO3) C,H,N.

DOSAGE: greater than 50 mg.

DURATION: unknown.

QUALITATIVE COMMENTS: (with 50 mg) There were no effects.

EXTENSIONS AND COMMENTARY: This was the first of the ethoxy homologues of TMA-2, and it was immediately (well, within a couple of months) run up from an initial dab to 25 milligrams. This was in early 1963, and the lack of activity of EMM was keenly disappointing. This was a level at which the prototype, TMA-2, was very active, and the conclusion was that maybe any change on the molecule would result in a loss of activity. So this approach was shelved for a while, and all efforts were directed into the relocation, rather than the elongation, of the methoxy groups. A few months later, the ethoxy question was addressed again, and the discovery of MEM rekindled full interest in this ethoxy question.


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