p-Toluenesulfonic acid → 1-[2-(4,5-Diphenyloxazol-2-yl)ethylamino]-1,2,3,4-tetrahydro-5-hydroxynaphthalene

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Reaction Steps

A solution of 5-(t-butyldiphenylsilyloxy)-1-oxo-1,2,3,4-tetrahydronaphthalene (0.52 g), 2-(4,5-diphenyloxazol-2-yl)ethylamine (0.33 g) and p-toluenesulfonic acid (catalytic amount) in toluene (30 ml) was refluxed for 15 hours with Dean-stark equipment. The solution was evaporated in vacuo and MeOH (10 ml) was added to the residue. To the MeOH solution, NaBH4 (0.21 g) was added at 0° C. After being stirred for 30 minutes at room temperature, the solution was evaporated in vacuo. The residue was partitioned between ethyl acetate and water. The organic layer was washed with brine. The dried solvent was evaporated in vacuo, and the residue was purified by chromatography on silica gel to give 1-[2-(4,5-diphenyloxazol-2-yl)ethylamino]-1,2,3,4-tetrahydro-5-(t-butyldiphenylsilyloxy)naphthalene (0.25 g) and 1-[2-(4,5-diphenyloxazol-2-yl)ethylamino]-1,2,3,4-tetrahydro-5-hydroxynaphthalene (0.11 g). To a solution of 1-[2-(4,5-diphenyloxazol-2-yl)ethylamino]-1,2,3,4-tetrahydro-5-(t-butyldiphenylsilyloxy)naphthalene (0.25 g) in THF (2 ml) was added 1M-THF solution (2 ml) of tetra-n-butyl ammonium fluoride (TBAF). After being stirred for 1 hour at room temperature, the reaction mixture was partitioned between ethyl acetate and sat. NaHCO3. The organic layer was washed with brine. The dried solvent was evaporated in vacuo. The residue was purified by chromatography on silica gel to give 1-[2-(4,5-diphenyloxazol-2-yl)ethylamino]-1,2,3,4-tetrahydro-5-hydroxynaphthalene (0.06 g).

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