Formic Acid → 4,4-Dimethyl-3,4-dihydroisoquinoline

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A mixture of 2-methyl-2-phenylpropylamine (7 g, 0.047 mol) and 96% formic acid (11 ml) was slowly heated to 200° C. and kept at this temperature for 1.25 hours during which time excess formic acid and water was allowed to distil. This mixture was added at 160° C. to a mixture of polyphosphoric acid (51 g) and phosphorous pentoxide (10.5 g) that had previously been heated at 170-180° C. for 1 hour. The resultant mixture was heated at 175° C. for 2 hours, before being cooled slightly and poured into water (500 ml) with stirring. The mixture was washed with ethyl acetate and the aqueous layer basified with 40% aqueous sodium hydroxide and extracted with dichloromethane (3×200 ml). Combined halogenated organics were dried (Na2SO4) and evaporated in vacuo to afford the title compound as a brown oil (5.95 g, 79%).

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