Hydrogen Bromide → 1,2,3,6-Tetrahydro-1-methyl-4-(2,4,6-trimethoxyphenyl)-3-pyridinol

Participants

Reaction Conditions

Reaction Steps

75.7 ml (0.44 mol) of 33% strength HBr in glacial acetic acid were added to 100 ml of glacial acetic acid and 50 g (0.44 mol) of 1-methylpiperidin-4-one (III) were then vigorously added dropwise at 20-25° C. with ice-cooling. 70.4 g (0.44 mol) of bromine were added dropwise at 20-25° C. under nitrogen in the course of 30 min to the suspension of the hydrobromide obtained in this way, a clear, yellowish solution being obtained. This was stirred at 25° C. for a further 60 min and 67.2 g (0.40 mol) of 1,3,5-trimethoxybenzene (V) were then added to the reaction solution. It was then stirred at 25° C. for 1 h. After this, 400 ml of water were allowed to run in and the mixture was heated to reflux for 3 h. The reaction mixture was allowed to stand at room temperature overnight, diluted with 400 ml of water and then cooled to 10° C., and a total of 320 ml of conc. sodium hydroxide solution were added dropwise at this temperature in the course of 4 h to the well stirred mixture (pH after addition 10.7). In the course of this the allyl alcohol (VII) first precipitated in slightly oily form, but then on longer stirring became solid and could readily be filtered off with suction. The dark yellow precipitate was filtered off with suction, washed with water and dried well. The crude product was then stirred with 80 ml of acetone, filtered off with suction and dried in vacuo.

Provenance & Evidence