Acetic Acid → 5-Methoxy-3-(N-methylthioethyl-N-propionylamino)chroman

Participants

Reaction Steps

To a solution of the appropriate amine (400 mg, 2.27 mmol) and acetic acid (400 mg, 6.99 mmol) in absolute ethanol (10 ml) was added 5-methoxy-3-chromanone (250 mg, 1.40 mmol), followed by 2-methylthioethylamine (0.6 ml, 6.41 mmol). The solution was stirred with 4 Å molecular sieve for 1 hour 15 min. MeOH (25 ml) was added to the reaction mixture and sodium cyano-borohydride (1.5 g, 23.6 mmol) dissolved in MeOH (10 ml). The reaction mixture was stirred for 30 min, water was added (50 ml) and pH adjusted with 5% aqueous NaOH to 11. The mixture was extracted with CH2Cl2. The phases were separated and the organic layer washed with water, dried (Na2SO4) and the solvent was evaporated. The crude product was immediately propionylated with propionyl chloride (0.5 ml, 5.72 mmol) in CH2Cl2 (20 ml) containing triethylamine (1 ml, 7.2 mmol). The reaction mixture was stirred for 30 min, washed with aqueous sodium carbonate solution, 1N HCl and water. The organic layer was separated and dried (MgSO4). The solvent was evaporated and the crude product chromatographed (SiO2) with light petroleum-ether (1:1) as eluant yielding 276 mg (64%) of the product as an oil. GC/MS (HP-5970A), m/e=310 (0.2) M+, 162 (100), 161 (54), 163 (50), 192 (22).

Provenance & Evidence