Ethyl bromoacetate → (5-Methyl-4-triisopropylsilanyloxymethyl-furan-2-yl)-acetic acid ethyl ester

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A solution of triisopropyl-(2-methyl-furan-3-ylmethoxy)-silane (14) (5.0 g) in tetrahydrofuran (15 mL) was cooled to −78° C. with stirring. This solution was treated drop-wise with n-butyl lithium (2.5 M in hexanes, 8.94 mL). The resulting solution was warmed to 0° C. and allowed to stand for 30 minutes after which a solution of dried zinc chloride (3.04 g) in tetrahydrofuran (10 mL) was added and the resulting solution allowed to stand for a further 1 hour at room temperature. Concurrently, a second reaction vessel was charged with tetrahydrofuran (10 mL), nickel(II) acetylacetonate (120 mg), and triphenylphosphine (122 mg) and cooled (−5° C.). Ethyl bromoacetate (1.03 mL) was added to this mixture, followed by the addition of the previously prepared solution of the furyl-zinc chloride. The resulting reaction mixture was allowed to warm to room temperature then stirred for a further 16 hours at room temperature. The reaction was quenched by the addition of saturated ammonium chloride solution (100 mL) and extracted with ethyl acetate (3×150 mL). The combined organic extracts were successively washed with water (200 mL) and brine (250 mL), dried, filtered and concentrated in vacuo. The residue was purified by flash chromatography using a gradient elution (diethyl ether/petroleum ether (40-60°) 1:49 to 1:25 by volume) to give compound 29 as a clear oil (1.44 g). LC/MS System A: Rt=5.16 min.

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