1-(Ethoxycarbonylmethyl)piperazine

Step A: tert-butyl 4-ethoxycarbonylmethyl-piperazine-1-carboxylate

Tert-butyl piperazine-1-carboxylate (2.62 g, 14 mmol), cesium carbonate (5 g, 15 mmol) and bromoacetic acid ethyl ester (1.56 ml, 14 mmol) were stirred at room temperature for 1 hour. The mixture was dissolved in water (200 ml) and ethyl ether (2 x 100 ml) was partitioned between them. The combined organic phases were dried over magnesium sulfate and concentrated to give yellow oil, which was crystallized to give tert-butyl 4-ethoxycarbonylmethyl-piperazine-1-carboxylate (2.6 g) in the form of a pale yellow solid.

1H N.M.R (CDCl3) = 1.24 (3H, t, J = 7.1 Hz), 1.43 (9H, s), 2.49 (4H, t, J = 5 Hz), 3.20 (2H, s), 3.44 (4H, t, J = 4.8 Hz), 4.16 (2H, q, J = 7.1 Hz).

Step B: 1-(Ethoxycarbonylmethyl)piperazine

A solution of tert-butyl 4-ethoxycarbonylmethyl-piperazine-1-carboxylate in 90% trifluoroacetic acid (5 ml) was stirred for 3 hours. The mixture was alkalized with saturated sodium bicarbonate solution and concentrated. The residue was ground with ethyl acetate (30 ml) and filtered. The filtrate was concentrated to give 1-(ethoxycarbonylmethyl)piperazine in the form of a yellow oil (about 1.5 g).