Benzathine → Ethyl 1,4-dibenzylpiperazine-2-carboxylate

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Reaction Conditions

Reaction Steps

A solution of ethyl 2,3-dibromopropionate (6 mL) in anhydrous toluene (50 mL) was added to a solution of N,N′-dibenzylethylenediamine (5 g) and DIPEA (12 mL) in anhydrous toluene (50 mL) under a Nitrogen atmosphere. The resulting mixture was heated to 100° C. for 21 hours, then allowed to cool to r.t., diluted with AcOEt (100 mL) and washed with brine (3×100 mL). The organic extract was dried and concentrated in vacuo to a residue which was purified by flash chromatography (CH/AcOEt 9:1) to give ethyl 1,4-dibenzyl-piperazine-2-carboxylate (5.65 g) as a yellow oil, which was used without any purification in the next step. Diisobutylaluminium hydride (1M in toluene-29 mL) was dropped into a solution of ethyl 1,4-dibenzyl-piperazine-2-carboxylate (5.47 g) in anhydrous toluene (110 mL) previously cooled to −78° C. under a Nitrogen atmosphere. The solution was stirred at −78° C. for 1 hour, then a 20% sodium hydroxide solution (20 mL) was added and the mixture was allowed to warm to r.t. Further 20% sodium hydroxide solution (50 mL) was added and the solution was extracted with Et2O (2×150 mL). The combined organic extracts were dried and concentrated in vacuo to give the title compound (5.33 g) as a crude, which was used without any further purification in the next step.

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