Ethyl bromoacetate → Ethyl (5-methoxy-2,3-dihydro-1H-inden-1-ylidene)ethanoate

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Reaction Steps

To a solution of 5-methoxyindanone (150 g, 0.91 mol) in anhydrous tetrahydrofuran (4.5 L), was added zinc (30 mesh, 103.64 g, 1.59 mol) and copper(I) chloride (4.53 g, 0.045 mol). The suspension was stirred under argon atmosphere and refluxed for 15 min; approximately a 25% portion of ethyl bromoacetate (133 mL, 1.18 mol) was added to the refluxing mixture in a slow dropwise fashion. After allowing to cool and stirring for 12 h at rt; TLC showed the presence of desired product. The remainder of ethyl bromoacetate was added dropwise; an exotherm was observed (internal temperature increased to 35° C.). After 4 h, TLC showed complete reaction. After the solids settled to the bottom of the flask, the liquid was siphoned off leaving a small amount behind to cover the solids. The flask was re-charged with 5-methoxyindanone (157.6 g, 1.86 mol total), anhydrous tetrahydrofuran (4.5 L), and zinc (80.92 g, 2.73 mol total). Ethyl bromoacetate (140 mL, 2.36 mol) was added dropwise. An exotherm was observed (internal temperature increased to 35° C.). When the stirred mixture was cooled to rt, TLC showed the reaction to be complete. The solids were allowed to settle and the liquid was siphoned off. The combined reaction solutions were concentrated under reduced pressure to a volume of about 2 L. The liquid was then poured into HCl (1 N aqueous solution, cooled in ice water) to bring the pH to 1. The product was extracted with ethyl acetate (2×1 L, 1×500 mL). The combined extracts were washed with water (1 L), brine (1 L), dried over Na2SO4, filtered, and concentrated under reduced pressure to afford a dark red oil which solidified gradually (438.3 g; theoretical yield=432 g). 1H NMR (CDCl3): δ 7.5 (d, 1H), 6.8 (m, 2H), 6.2 (t, 1H), 4.2 (q, 2H), 3.8 (s, 3H), 3.3 (m, 2H), 3.0 (t, 2H), 1.3 (t, 3H). MS (Cl) m/z 233 [M+H]+.

Provenance & Evidence