Dimethyl malonate → Dimethyl 2-(2-bromoallyl)malonate

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To a suspension of sodium hydride (5.0 g, 125 mmol) in HMPA (50 ml, distilled from calcium hydride) was added a solution of dimethyl malonate (11.7 ml, 100 mmol) in HMPA (5 ml) at 0° C. under argon. The mixture was heated to 50° C. and stirred 1 hour. Following this the solution was again cooled to 0° C., and a solution of 2,3-dibromopropene (12.2 ml, 100 mmol) in HMPA (5 ml) was added to the reaction mixture. Next, the solution was warmed to 40° C. and stirred for 1 hour. The reaction mixture was quenched with aq. HCl (10%, 88 ml) and extracted with ether (3×45 ml). The organic fractions were collected, dried over MgSO-4, and the solvent was removed in vacuo. The crude oil was purified via silica gel chromatography (eluants: chloroform/hexane) to obtain the titled product as a colorless oil (16.3 g, 65%). 1H-NMR (300 MHz, CDCl3) δ 5.70 (d, J=1.8 Hz, 1 H), 5.48 (d, J=1.8 Hz, 1H), 3.63 (t, J=7.5 Hz, 1 H), 3.76 (s, 6 H), 3.04 (d, J=7.5 Hz, 2 H).

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