2C-T-7 Synthesis

Taken from PIHKAL by Alexander Shulgin

To a solution of 3.4 g of KOH pellets in 50 mL hot MeOH, there was added a mixture of 6.8 g 2,5-dimethoxythiophenol (see under the recipe for 2C-T-2 for its preparation) and 7.4 g (n)-propylbromide dissolved in 20 mL MeOH. The reaction was exothermic, with the deposition of white solids. This was heated on the steam bath for 0.5 h, added to 800 mL H₂O, additional aqueous NaOH added until the pH was basic, and extracted with 3x75 mL CH₂Cl₂. The pooled extracts were washed with dilute NaOH, and the solvent removed under vacuum. The residue was 2,5-dimethoxyphenyl (n)-propyl sulfide which was obtained as a pale yellow oil, and which weighed 8.9 g. It had a light pleasant fruity smell, and was sufficiently pure for use in the next reaction without distillation.

A mixture of 14.4 g POCl3 and 13.4 g N-methylformanilide was heated for 10 min on the steam bath. To this claret-colored solution was added 8.9 g of 2,5-dimethoxyphenyl (n)-propyl sulfide, and the mixture heated an additional 25 min on the steam bath. This was then added to 800 mL of well-stirred warm H₂O (pre-heated to 55 °C) and the stirring continued until the oily phase had completely solidified (about 15 minutes). The resulting brown sugar-like solids were removed by filtration, and washed with additional H₂O. After sucking as dry as possible, they were dissolved in an equal weight of boiling MeOH which, after cooling in an ice-bath, deposited pale ivory colored crystals. After filtration, modest washing with cold MeOH, and air drying to constant weight, there was obtained 8.3 g of 2,5-dimethoxy-4-(n-propyl-thio)benzaldehyde with a mp of 73-76 °C. Recrystallization from 2.5 volumes of MeOH provided a white analytical sample with mp 76-77 °C. The NMR spectrum in CDCl3 was textbook perfect, with the two aromatic protons showing singlet signals at 6.81 and 7.27 ppm, giving assurance that the assigned location of the introduced aldehyde group was correct.

To a solution of 4.0 g 2,5-dimethoxy-(n-propylthio)benzaldehyde in 20 g of nitromethane there was added 0.23 g of anhydrous ammonium acetate, and the mixture was heated on the steam bath for 1 h. The clear orange solution was decanted from some insoluble material and the excess nitromethane removed under vacuum. The orange-yellow crystalline material that remained was crystallized from 70 mL boiling IPA which, on slow cooling, deposited 2,5-dimethoxy-beta-nitro-4-(n)-propylthiostyrene as orange crystals. After their removal by filtration and air-drying to constant weight, they weighed 3.6 g, and had a mp of 120-121 °C. Anal. (C13H17NO4S) C,H.

A solution of LAH (132 mL of a 1 M solution in THF) was cooled, under He, to 0 °C with an external ice bath. With good stirring there was added 3.5 mL 100% H₂SO₄ dropwise, to minimize charring. This was followed by the addition of 8.4 g 2,5-dimethoxy-beta-nitro-4-(n)-propylthiostyrene in 50 mL anhydrous THF. There was an immediate loss of color. After a few min further stirring, the tem-perature was brought up to a gentle reflux on the steam bath, then all was cooled again to 0 °C. The excess hydride was destroyed by the cautious addition of IPA (21 mL required) followed by sufficent 5% NaOH to give a white granular character to the oxides, and to assure that the reaction mixture was basic (15 mL was used). The reaction mixture was filtered and the filter cake washed first with THF and then with IPA. The filtrate and washes were combined and stripped of solvent under vacuum providing about 6 g of a pale amber oil. Without any further purification, this was distilled at 140-150 °C at 0.25 mm/Hg to give 4.8 g of product as a clear white oil. This was dissolved in 25 mL IPA, and neutralized with concentrated HCl forming immediate crystals of the hydrochloride salt in the alcohol solvent. An equal volume of anhydrous Et₂O was added, and after complete grinding and mixing, 2,5-dimethoxy-4-(n)-propylthiophenethylamine hydrochloride (2C-T-7) was removed by filtration, Et₂O washed, and air dried to constant weight. The resulting spectacular white crystals weighed 5.2 g.

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