Lithium diisopropylamide → 4-(2-Cyclopentyl-1-methoxycarbonyl-ethyl)-benzoic acid methyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of freshly prepared lithium diisopropylamide (2.3 mL of a 0.31M stock solution, 0.71mmol) cooled to −78° C. was treated with a solution of 4-methoxycarbonylmethyl-benzoic acid methyl ester (66 mg, 0.31 mmol) in tetrahydrofuran/1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (0.85 mL, 3:1). The resulting solution was stirred at −78° C. for 45 min. At this time, the reaction was treated with a solution of iodomethylcyclopentane (86 mg, 0.40 mmol) in 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (1 mL). The reaction mixture was stirred at −78° C. for 4 h. The reaction was then warmed to 25° C. and stirred at 25° C. for 18 h. At this time, the reaction mixture was quenched by the slow addition of a saturated aqueous ammonium chloride solution (10 mL). The reaction mixture was then poured into water (50 mL). This solution was extracted into ethyl acetate (3×25 mL). The organics were dried over sodium sulfate, filtered, and concentrated in vacuo. Flash chromatography (Merck Silica gel 60, 230-400 mesh, 80/20 hexanes/ethyl acetate) afforded 4-(2-cyclopentyl-1-methoxycarbonyl-ethyl)-benzoic acid methyl ester (60.5 mg, 65.7%) as a clear oil: EI-HRMS m/e calcd for C17H22O4(M+) 290.1518, found 290.1518.

Provenance & Evidence