Synthesis
The general procedure for the synthesis of methyl 2,2-dimethyl-3-oxopropionate from methyl hydroxytrimethylacetate was as follows: first, the first intermediate compound, methyl 3-[6-chloro-2-(2,2-dimethyl-propionylamino)-pyridin-3-yl]-3-hydroxy-2,2-dimethyl-propionate, was prepared. This was done as follows: to a stirred solution of oxalyl chloride (11.0 g, 87.0 mmol) in dichloromethane (180 mL) was slowly added a solution of DMSO (12.9 mL, 182 mmol) in dichloromethane (40 mL) at -60 °C. The resulting solution was stirred for 5 minutes and then a dichloromethane (10 mL) solution of methyl 2,2-dimethyl-3-hydroxypropionate (10.0 g, 75.6 mmol) was added dropwise over 10 minutes. The cloudy mixture was continued to be stirred for 15 minutes, followed by the dropwise addition of triethylamine (52 mL, 380 mmol) and keeping the reaction temperature at -50°C or lower. After stirring for 5 minutes, the mixture was slowly warmed to room temperature. Next, water (200 mL) was added for quenching. The organic and aqueous layers were separated and the aqueous layer was extracted with dichloromethane (2 x 100 mL). The combined organic layers were washed sequentially with 1 M HCl (100 mL), water (100 mL), saturated NaHCO3 solution (100 mL), water (100 mL) and brine (100 mL), then dried with Na2SO4, filtered and concentrated. Most of the solvent was removed under vacuum and only a small amount of dichloromethane was retained to minimize loss of volatile products. The crude product was purified by vacuum distillation to afford the target product methyl 2,2-dimethyl-3-oxopropionate (8.1 g, 83% yield, boiling point 89 °C, pressure about 80 mmHg). The 1H NMR (CDCl3) data of the product were as follows: δ 9.67 (s, 1H), 3.76 (s, 3H), 1.36 (s, 6H).
References
[1] Patent: WO2017/68089, 2017, A2. Location in patent: Page/Page column 240
[2] Chemistry - A European Journal, 1999, vol. 5, # 1, p. 121 - 161
[3] Patent: WO2012/119559, 2012, A1. Location in patent: Page/Page column 105-106
[4] Tetrahedron Asymmetry, 2003, vol. 14, # 21, p. 3371 - 3378
[5] Patent: US2005/43309, 2005, A1. Location in patent: Page/Page column 78
