Ammonia → (R)-2-(4-Methanesulfonyl-3-methyl-pyridin-2-ylmethanesulfinyl)-1H-benzimidazole

Participants

Reaction Conditions

Reaction Steps

To a mixture of 2-(4-methanesulfonyl-3-methyl-pyridineylmethylsulfonyl)-1-H-benzimidazole (25 g), tetrahydrofuran (625 ml) and water (0.08 gm) was added (+)-diethyl-L-tartrate (31 gm) under nitrogen atmosphere and heated to 50 to 60° C. Subsequently, Ti(IV)isopropoxide (21.3 gm) was added to the reaction mixture at 50 to 60° C. and maintained at the same temperature for about 45-60 min. The reaction mixture was cooled to 20-25° C. and diisopropylethylamine (9.7 g) was added and maintained at the same temperature for 10-15 min. Cumene hydroperoxide (80% 15 ml) was then added to the reaction mixture and maintained at the same temperature for 2 hours. To the reaction mixture was added 10-12% aq. ammonia solution (100 ml) and maintained for 15 min. The layers were separated and 10-12% aq. ammonia solution (100 ml) was added to the organic layer at 20-25° C., maintained for 15 min and the steps repeated for two or three times. Combined all the aq. ammonia solution layers and cooled to 0-10° C. Adjusted the pH of the reaction mixture to 7.0 to 7.5 with acetic acid (125 ml) at 0 to 10° C. Distilled off the tetrahydrofuran traces at 40° C. under reduced pressure. Cooled the reaction mixture to 0 to 10° C. and maintained at the same temperature for about one to two hours. Filtered the solid and washed with DM water (50 ml) and dried to give 18 g of the title compound.

Provenance & Evidence