Dimethyl (2-oxopropyl)phosphonate → methyl(3E)-2,2-dimethyl-5-oxohex-3-enoate

To a solution of dimethyl (2-oxopropyl)phosphonate (4.09 mL, 30 mmol) in tetrahydrofuran (200 mL) at 0° C. was added potassium tert-butoxide (3.22 g, 28.7 mmol). After 15 minutes, the reaction flask was moved to a 20° C. water bath and then a solution of methyl 2,2-dimethyl-3-oxopropanoate (3.39 g, 26 mmol) in tetrahydrofuran (10 mL) was added. After 20 hours, the opaque reaction mixture was partitioned between diethyl ether (100 mL) and water (100 mL). The layers were separated and the aqueous layer was extracted with diethyl ether (1×100 mL, 1×50 mL). The combined organic layers were washed with saturated aqueous sodium bicarbonate solution and brine, dried over sodium sulfate, filtered, and concentrated. The residue was purified by silica gel flash column chromatography (0-4% methanol/dichloromethane gradient) to afford methyl (3E)-2,2-dimethyl-5-oxohex-3-enoate (2.21 g, 12.21 mmol, 47% yield) as a light yellow oil. 1H NMR (500 MHz, CDCl3) δ 6.95 (d, J=16.3, 1H), 6.09 (d, J=16.3, 1H), 3.71 (s, 3H), 2.29 (s, 3H), 1.37 (d, J=2.3, 614).