Diethyl Malonate → Diethyl 3,3-dimethoxycyclobutane-1,1-dicarboxylate

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Diethyl malonate (14.3 ml, 94.20 mmol) was added to a stirred suspension of sodium hydride (4.75 g, 98.90 mmol, 50% dispersion in oil) in N,N-dimethylformamide (40 ml) at a rate such that the temperature was maintained below 40° C. On cessation of hydrogen evolution, the 1,3-dibromo-2,2-dimethoxy-propane (12.34 g, 47.09 mmol) was added in one portion and the reaction was heated at 135° C. for 48 h. To the cooled reaction was added an aqueous solution of ammonium chloride (100 g in 1.6 L) and extracted with hexane (4×50 ml). The combined extracts were then washed with water and aqueous saturated sodium bicarbonate solution, dried over magnesium sulfate and concentrated in vacuo. Unreacted 1,3-dibromo-2,2-dimethoxy-propane (6.9 g) was recovered by recrystallization from methanol. The filtrate was evaporated and more volatile fractions were removed by distillation under reduced pressure affording 3,3-dimethoxy-cyclobutane-1,1-dicarboxylic acid diethyl ester (3.05 g, 25%) as a light yellow oil: 1H NMR (300 MHz, CDCl3) δ ppm 1.26 (t, J=6.9 Hz, 6H, 2×CH3), 2.73 (s, 4H, 2×CH2), 3.15 (s, 6H, 2×OCH3), 4.22 (q, J=6.9 Hz, 4H, 2×OCH2).

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