Intermediate VIII: Steps for the synthesis of methyl 8-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylate:
Step a) Preparation of methyl 8-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylate: to a methanolic solution of 8-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (16 g, 0.084 mol) was added sulfoxide chloride (23 g, 0.2 mol). The reaction mixture was stirred at room temperature for 12 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate (200 mL), the organic layer was washed with 10% aqueous sodium bicarbonate, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give methyl 8-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylate 16 g (94% yield) as a liquid. Thin layer chromatography (TLC) conditions: chloroform/methanol (9/1, v/v), Rf = 0.9.
