Benzyl Bromide → ethyl 2-benzyl-5-(4-benzyloxyphenyl)-2H-pyrazole-3-carboxylate

Participants

Reaction Steps

Ethyl 5-(4-benzyloxyphenyl)-2H-pyrazole-3-carboxylate (6 g) is added portionwise to a stirred suspension of sodium hydride (0.75 g) in tetrahydrofuran (250 mL) at room temperature. Stirring is continued at this temperature for a further 30 minutes when benzyl bromide (3.57 g) is added in one portion. The reaction mixture is heated to reflux for 5 hours, then evaporated in vacuo. The residue is treated with water (250 mL), the resulting yellow solid washed well with water, then dissolved in tetrahydrofuran and filtered to remove a small amount of insoluble white solid. The filtrate is evaporated and the residual yellow solid purified by flash chromatography on silica eluting initially with dichloromethane then with a mixture of ethyl acetate and dichloromethane (1:9 v/v) to give ethyl 2-benzyl-5-(4-benzyloxyphenyl)-2H-pyrazole-3-carboxylate (1.2 g) and ethyl 1-benzyl-5-(4-benzyloxyphenyl)-2H-pyrazole-3-carboxylate (2 g).

Provenance & Evidence