Potassium Hydroxide → 8-Ethyl-2-methyl-5-[2-(5-methyl-pyrazin-2-yl)-ethyl]-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole

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Reaction Steps

To a solution of 8-Ethyl-2-methyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole (0.054 g. 0.25 mmol) in N-methyl 2-pyrolidone (2.0 mL) was added powdered potassium hydroxide (0.112 g, 0.002 mol) and allowed to stir for 10 min at RT. 2-methyl-5-vinyl pyrazine (0.033 g, 0.75 mmol) was added and stirred for further 1 h. at 60 deg C. After completion (TLC), reaction mixture was diluted with water (20 mL) and extracted with ethyl acetate (3×50 mL). The organic layer was dried over anhydrous sodium sulphate and concentrated under reduced pressure using rotary evaporator. The crude was purified through column chromatography (7% MeOH:DCM in silica 100-200 mesh, Diameter of column—2.5 cm, Height of silica—approx. 5 inch) to provide the desired compound as yellow oil (0.05 g, 60% yield). 8-Ethyl-2-methyl-5-[2-(5-methyl-pyrazin-2-yl)-ethyl]-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole (0.05 g, 0.000149 mol) was dissolved in THF (1.0 mL). A solution of oxalic acid dihydrate (0.019 g, 0.00014 9 mol) in THF (1.0 mL) was added and stirred for 30 min at RT, Precipitate obtained was filtered and dried to give oxalate salt as off white solid (0.035 g, 50% yield).

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