To a mixture of S6 (140 mg, 0.285mmol) and tert-butyldimethylsilyl chloride (TBSCl, 86.0 mg, 0.570 mmol)in THF (5.7 mL) was added dropwise potassium bis(trimethylsilyl)amide (KHMDS,0.5 M solution in toluene, 2.0 mL) at –78 °C, and the resulting mixture was stirred for 3 h. The reaction was quenched with saturated aqueous ammonium chloride. The mixture was extracted with ethyl acetate and the combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated in vacuo. Purification of the residue by flash column chromatography using diol silica gel (DIOL MB 100-40/75) with ethyl acetate/n-hexane(1:4) afforded 6 (148 mg, 86%) as a colorless oil.
Reference: Org. Lett. 2014, 16, 768-771.
In a 50 mL round bottomed flask methyl acetoacetonate (20.0 g,172 mmol, 1.0 eq), trimethylorthoformate (18.6 g, 175 mmol, 1.0 eq) and concentrated H2SO4 (6 drops) were added and stirred at 20°C for 24 h. After this time, a slight excess of quinoline (12 drops) was added to neutralize the acid. Distillation under reduced pressure afforded the(E)-methyl-3- methoxybut-2-enoate 15a. Colourless liquid, yield (19.5 g, 149mmol,87% yield).
Reference: J.Am.Chem.Soc. 2012, 134, 19362-19365