tert-butyl 4-(2-ethoxy-1,1-difluoro-2-oxoethyl)-4-hydroxypiperidine-1-carboxylate synthesis

Yield:635698-99-6 76%

Reaction Conditions:

Stage #1: Ethyl bromodifluoroacetatewith zinc in tetrahydrofuran at 20; for 0.0833333 h;Heating / reflux;
Stage #2: N-tert-butyloxycarbonylpiperidin-4-one in tetrahydrofuran; for 2 h;Heating / reflux;

Steps:

24

Powdered zinc (2.82 g, 0.043 mol) was suspended in tetrahydrofuran (50.0 mL) under flow of argon gas, and the suspension was mixed with ethyl bromodifluoroacetate (7.31 g, 0. 036 mol) at room temperature, followed by stirring under reflux for five minutes. The mixture was further mixed with a solution of tert-butyl 4-oxopiperidinecarboxylate in tetrahydrofuran (3.00mol/L, 10. 0 mL, 0.030 mol), followed by stirring under reflux for two hours. After checking the completion of the reaction by thin layer chromatography, the reaction mixture was mixed with ethyl acetate and diluted hydrochloric acid (1.00mol/L), followed by separation. The organic layer was sequentially washed with a saturated aqueous sodium bicarbonate solution and brine, was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (hexane:chloroform=1:9) and thereby yielded tert-butyl 4-(ethoxycarbonyldifluoromethyl)-4-hydroxy-piperidinecarboxylate (7.39 g, 76%).

References:

EP1552842,2005,A1 Location in patent:Page/Page column 312