Dimethylformamide → 1,1-Bis(propan-2-yl) 3,3-dimethoxycyclobutane-1,1-dicarboxylate

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Reaction Steps

To a stirred suspension of sodium hydride (96.5 g, 2.413 mol, 60% in mineral oil) in dry N,N-dimethylformamide (900 ml) was added 1,3-bis(propan-2-yl) propanedioate (363.3 g, 1.930 mol) dropwise under nitrogen at a rate such that the temperature was maintained below 70° C. On cessation of hydrogen evolution, the mixture was heated to 130° C., to 3-dibromo-2,2-dimethoxypropane (252.8 g, 0.965 mol) was then introduced in one portion. The mixture was heated under reflux for 48 hours. The cooled mixture was poured into a saturated aqueous solution of ammonium chloride (300 mL) and extracted with methyl tert-butyl ether (300 mL). The organic layer was washed with a saturated aqueous solution of sodium bicarbonate and brine, dried over sodium sulfate, and concentrated in vacuo. The residue was distilled in vacuo (oil pump) to afford 52.7 g of dipropan-2-yl 3,3-dimethoxycyclobutane-1,1-dicarboxylate as a colorless oil (yield was 58.2%). 1H NMR (400 MHz, CDCl3) δ ppm 5.02 (m J=6.4 Hz, 2 H), 3.12 (s, 6 H), 2.66 (s, 4 H), 1.11 (d, J=6.4 Hz, 12 H).

Provenance & Evidence