Trifluoroacetic anhydride → 2,8-Dimethyl-4-naphthalen-2-yl-1,2,3,4-tetrahydroisoquinoline

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Reaction Steps

The product from Step A (1.25 g, 4.1 mmol) was dissolved in trifluoroacetic acid (TFA, 7.5 mL), then trifluoroacetic anhydride (TFAA, 7.5 mL) was added. After stirring for 24 h, the solvents were removed in vacuo, the residue was dissolved in MeOH, and the solvent was removed in vacuo. The residue was dissolved in aqueous NH4OH, then extracted twice with CH2Cl2. The extract was dried over Na2SO4, filtered, the solvent was removed in vacuo, and the residue was purified by column chromatography on silica gel (40 g) eluting with 5% to 30% EtOAc/hexanes with 1% Et3N to give 2,8-dimethyl-4-naphthalen-2-yl-1,2,3,4-tetrahydroisoquinoline (0.73 g, 61%) as a clear, dark yellow oil: 1H NMR (300 MHz, CDCl3) δ 7.66-7.88 (m, 4 H), 7.38-7.48 (m, 2 H), 7.26 (dd, J=8.3, 1.6 Hz, 1 H), 6.93-7.04 (m, 2 H), 6.74 (d, J=7.2 Hz, 1 H), 4.45 (t, J=6.9 Hz, 1 H), 3.75 (d, J=15.4 Hz, 1 H), 3.51 (d, J=15.4 Hz, 1 H), 3.06 (ddd, J=11.2, 5.6, 0.9 Hz, 1 H), 2.67 (ddd, J=11.4, 8.5 Hz, 1 H), 2.48 (s, 3 H), 2.27 (s, 3H).

Provenance & Evidence