1-Bromo-4-ethylbenzene → Ethyl 4-[[4-(4-ethylphenyl)-2,2-dimethyl-(2h)-thiochromen-6-yl]ethynyl]-benzoate

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Reaction Steps

A solution of 4-ethylbromobenzene (670.9 mg, 3.63 mmol) in 4.0 mL of THF was cooled to −78° C. and tert-butyllithium (464.5 mg, 7.25 mmol, 4.26 mL of a 1.7M solution in pentane) was added to give a yellow solution. After 30 minutes, a solution of ZnCl2 (658.7 mg, 4.83 mmol) in 8.0 mL THF was slowly added via cannula. The resulting solution was warmed to room temperature and transferred via cannula to a solution of ethyl 4-(2,2-dimethyl-4-trifluoromethanesulfonyloxy-(2H)-thiochromen-6-ylethynyl)-benzoate (1.20 g, 2.42 mmol) and tetrakis(triphenylphosphine)palladium(0) (111.7 mg, 0.097 mmol) in 8.0 mL THF. This solution was heated to 50° C. for 1 hour, cooled to room temperature, and the reaction quenched by the addition of saturated aqueous NH4Cl. The solution was extracted with EtOAc and the combined organic layers were washed with H2O and saturated aqueous NaCl before being dried (MgSO4) and concentrated under reduced pressure. Ethyl 4-[[4-(4-ethylphenyl)-2,2-dimethyl-(2H)-thiochromen-6-yl]-ethynyl]-benzoate was isolated by column chromatography (5% EtOAc/hexanes) as a colorless oil.

Provenance & Evidence