Methyl p-toluenesulfonate → N-Methyl 3,4-dihydroisoquinolinium p-toluene sulfonate

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Reaction Conditions

Reaction Steps

The title compound was prepared using the procedure described by Koelsch et al in J. Am. Chem. Soc, (1953) 75, 2095. In a 250-mL one-necked round-bottomed flask equipped with a magnetic stir bar and a reflux condenser were placed 3,4-dihydroisoquinoline (8.27 grams, 63 mmol) and 40 ml of methanol. The mixture was stirred and cooled to 0° C. A solution of methyl p-toluenesulfonate (11.73g, 63 mmol) and 70 ml of methanol was added dropwise. The color of the solution remained clear and yellow. The mixture was heated to reflux for 6 hours. The methanol was then removed in vacuo to provide a quantitative yield (20 g) of an off-white solid (top 115°-119° C.). The solid was pulverized and washed with 40 ml of acetone at room temperature. Suction filtration provided a white solid in 88% yield: mp 124°-127° C. 1H NMR (D2O): δ2.27 (s,3H), 3.15 (t,2H), 3.73 (S,3H), 3.93 (t,2H), 7.18-7.78 (m,8H), 8.77 (s,1H). Impurities observed at 4.46 (s), 8.0-8.3 (m), 9.4 (s) were due to N-methyl-isoquinolinium p-toluenesulfonate.

Provenance & Evidence