Synthesis
GENERAL STEPS: A solution of dibenzylamine (0.3 mmol, dissolved in 4.0 mL of ether) was added to a solution of water (1.0 mL) containing Ru(II)-hm-pheox 3 (0.0075 mmol, 2.5 mol%), followed by the addition of ethyl diazidoacetate (0.3 mmol, 1.0 equiv). The two-phase reaction mixture was stirred at room temperature until the reaction was complete. At the end of the reaction, the ether layer was separated and removed by decantation, and the catalyst in the aqueous phase was washed three times with ether (3 x 5.0 mL). The combined ether phases contained the ethyl 2-(dibenzylamino)acetate product, which was dried over anhydrous Na2SO4 and concentrated under reduced pressure. In most cases, the purity of the product is sufficient and no further purification is required. The aqueous phase containing the catalyst can be recovered for reuse. For purification of the 2-piperazinone product, silica gel column chromatography was used, using only methanol as eluent.
References
[1] Tetrahedron Letters, 2017, vol. 58, # 51, p. 4750 - 4754
[2] Asian Journal of Chemistry, 2017, vol. 29, # 2, p. 349 - 352
[3] Tetrahedron Letters, 2014, vol. 55, # 40, p. 5417 - 5419
[4] Angewandte Chemie - International Edition, 2012, vol. 51, # 22, p. 5351 - 5354
[5] Tetrahedron Letters, 2009, vol. 50, # 31, p. 4467 - 4469
