Hydrochloric Acid → t-Butyl 3-(1-carboxycyclopentyl)propanoate

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Reaction Steps

To a stirred solution of lithium diisopropylamide (0.43 mole) in dry tetrahydrofuran (300 ml) at -20° C. under nitrogen atmosphere was added cyclopentane carboxylic acid (22.7 g; 0.20 mole). The solution was allowed to warm to room temperature and after 2 hours was cooled to -10° C. and added by cannula to a stirred solution of t-butyl 3-bromopropionate (44.4 g, 0.21 mole) in tetrahydrofuran (100 ml). The resulting solution was allowed to warm to room temperature and kept overnight. Hydrochloric acid (3N, 250 ml) was cautiously added, followed by diethyl ether (500 ml) and the layers allowed to separate. The aqueous layer was washed with diethyl ether (300 ml) and the ether layers were combined, washed with water (300 ml), dried over magnesium sulphate and evaporated to give an oil. The oil was taken up in diethyl ether (300 ml) and washed with saturated sodium hydrogen carbonate solution (3×100 ml) until no further cyclopentane carboxylic acid remained. The diethyl ether solution was then extracted with 10% sodium carbonate solution, (4×150 ml), the aqueous phase separated, acidified with 2N hydrochloric acid, and extracted with diethyl ether (3×200 ml). The diethyl ether layer was separated, washed with water (300 ml), dried over magnesium sulphate and evaporated to give an oil that readily crystallised. Recrystallisation from pentane gave a colourless solid (10.4 g, 21%) m.p. 78°-81° C. (from pentane). Found: C,64.70;; H,9.18. C13H22O4 requires: C,64.44; H,9.15%.

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