2-Methylbenzenesulfonic acid → dimethyl 1-(3-chloropyridin-2-yl)-1H-pyrazole-3,5-dicarboxylate

Participants

Reaction Conditions

Reaction Steps

One spatula tip of toluenesulphonic acid is added to a solution of 15.6 g (64.8 mmol) of dimethyl 2-pyrrolidino-4-oxo-2-pentenedicarboxylate and 20.4 g (64.8 mmol) of the toluenesulphonic acid salt of 3-chloro-2-pyridin-2-ylhydrazine in 84 ml of methanol and the mixture is heated at 50° C. for 5 h. It is then admixed with 12.3 g (64.8 mmol) of toluenesulphonic acid monohydrate and stirred initially at 50° C. for 1 h and under reflux for 1 h. After the mixture has cooled to 0° C., the precipitated crystals are filtered off with suction and filtration is carried out over silica gel (cyclohexane/ethyl acetate=1:1).

Provenance & Evidence