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0 °C

5,6-Dimethoxy-3-phenyl-1,2,3,4-tetrahydronaphthalene-1-carboxylic acid (5 g, 16 mmol), from Step 3, was suspended in 100 mL of toluene and 5 mL of oxalyl chloride was added. The reaction mixture was heated at reflux temperature for 1.5 h under a nitrogen atmosphere. The solvent was evaporated and excess reagents removed from the residue as an azeotrope with toluene (2×40 mL). The acid chloride and 2 g (20 mmol) of N,O-dimethylhydroxylamine hydrochloride was dissolved in 80 mL of ethanol-free chloroform. The solution was cooled to 0° C. and 3.3 mL of pyridine was added slowly. The reaction mixture was allowed to warm to ambient temperature and stirred at ambient temperature for approximately 4 h then evaporated to dryness. The residue was dissolved in a 1:1 mixture of diethyl ether and methylene chloride and washed with brine. The layers were separated and the organic layer dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give the title compound as an oil in 98% yield. The product of Step 4 was used in the next step without purification.

1. temperatureThe reaction mixture was heated
2. temperatureat reflux temperature for 1.5 h under a nitrogen atmosphere
3. customThe solvent was evaporated
4. customexcess reagents removed from the residue as an azeotrope with toluene (2×40 mL)
5. temperatureto warm to ambient temperature
6. customthen evaporated to dryness
7. dissolutionThe residue was dissolved in a 1:1 mixture of diethyl ether and methylene chloride
8. washwashed with brine
9. customThe layers were separated
10. dry with materialthe organic layer dried over anhydrous magnesium sulfate
11. filtrationfiltered
12. concentrationconcentrated under reduced pressure