To a solution of 543 mg (1.64 mmol) of ethyl 4-[(5,6,7,8-tetrahydro-8,8-dimethylnaphth-2-yl)ethynyl]benzoate (obtainable from Compound M by coupling with ethyl-4-iodobenzoate) in 20 ml of CCl4 was added 320 mg (1.81 mmol) of N-bromosuccinimide and 26 mg (0.11 mmol) of benzoyl peroxide. The mixture was refluxed for 3 hours under argon atmosphere, cooled, filtered through celite and concentrated in vacuo to a dark brown syrup. The syrup was taken up in 20 ml of dry THF and 780 mg (6.9 mmol) of potassium thioacetate was added. The mixture was refluxed for 4 hours under argon atmosphere, concentrated in vacuo and purified by chromatography (silica, 10% EtOAc-hexane) to yield the title compound as a pale yellow solid.
