Bromine → 3-Bromo-3-methylpiperidin-2-one

Participants

Reaction Conditions

Reaction Steps

A mixture of 5.15 g of 3-methyl-2-piperidone (Ber. 24 page 2445) and 50 ml of chloroform is chilled to about 0° C. Then there are added while stirring at 0°-5° C. 19 g of phosphorus pentachloride, followed by 0.2 g of anhydrous zinc chloride. The mixture is heated to about 15° C., treated dropwise with a solution of 2.5 ml of bromine in 5 ml of chloroform and then heated to 40° C. for 5 hours, while stirring. After cooling the mixture is poured on ice and treated with sodium hydrogensulfite until it is discolored. The layers are separated and the aqueous phase is extracted with chloroform. The combined chloroform layers are dried over magnesium sulfate and then the solvent is distilled off in vacuo. The semi-solid residue is recrystallized from acetone to give 3-bromo-3-methyl-2-piperidone melting at 107° to 109° C. in a yield of 81% of the theoretical.

Provenance & Evidence