Ethyl 4-iodobenzoate → Ethyl 4-[4,4-dimethylthiochroman-6-yl-ethynyl]benzoate

Participants

Reaction Conditions

Reaction Steps

Reaction vessels used in this procedure were flame dried under vacuum and all operations carried out in an oxygen-free, argon or nitrogen atmosphere. To a solution of 533.9 mg (2.6389 mmol) of 4,4-dimethyl-6-ethynylthiochroman (from Example 4) in 4 ml of dry tetrahydrofuran at 0° C. was added dropwise 1.7 ml of 1.6M (2.72 mmol) n-butyl lithium in hexane. This was stirred at 0° C. for 10 minutes and at room temperature for 15 minutes, cooled again to 0° C. and then treated with a solution of 410 mg (3.005 mmol) of fused ZnCl2 in 4 ml dry tetrahydrofuran using a double ended needle. Thereafter, the solution was stirred at 0° C. for 45 minutes, then at room temperature for 20 minutes. A solution of 724.4 mg (2.6243 mmol) of ethyl 4-iodobenzoate (from Example 5) in 4 ml dry tetrahydrofuran was transferred by double ended needle into a suspension of 520 mg (0.45 mmol) of tetrakistriphenylphosphine palladium in 5 ml dry tetrahydrofuran and stirred at room temperature for 20 minutes, then treated by double ended needle with the solution of the alkynyl zinc chloride prepared above. This mixture was stirred at room temperature for 18 hours, then quenched with ice and 30 ml 3N hydrogen chloride. Product was recovered by extraction with 3×75 ml ether. Ether fractions were combined and washed successively with saturated NaHCO3 and saturated NaCl solutions and dried (MgSO4). Solvent was removed in vacuo and the residue purified by flash chromatography (silica; 5% ethyl acetate in hexane) followed by HPLC (Whatman Partisil M-9 10/50; 4% ethyl acetate in hexane) to give the title compound as a colorless oil. PMR (CDCl3) :δ 1.36 (6H), 1.42 (3H, t, J~7 Hz), 1.93-1.99 (2H, m), 3.03-3.08 (2H, m), 4.40 (2H, q, J~7 Hz), 7.09 (1H, d, J~8.4 Hz), 7.22 (1H, dd, J~8.4 Hz, 2.1 Hz), 7.56 (1H, d, J~2.11 Hz), 7.59 (2H, d, J~7.8 Hz), 8.04 (2H, d, J~7.8 Hz).

Provenance & Evidence