Synthesis
GENERAL METHODS: N-methylmorpholine (NMM, 6.0 mmol) was slowly added dropwise to a stirred solution of 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT, 1.5 mmol) in anhydrous dichloromethane (CH2Cl2, 15 mL) under anhydrous conditions with continuous stirring for 10 min. Subsequently, Schiff base (1.0 mmol) and carboxylic acid (1.5 mmol) were added to the resulting white suspension of 4-(4,6-dimethoxytriazin-2-yl)-4-methylmorpholine hydrochloride (DMTMM salt) and the reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the mixture was washed sequentially with saturated sodium bicarbonate solution (NaHCO3, 15 mL) and brine (15 mL), dried over anhydrous sodium sulfate (Na2SO4) and subsequently concentrated under reduced pressure. The product was purified by silica gel short column chromatography (with ethyl acetate (EtOAc) as eluent) or by crystallization from 2-azetidinone (3l-m) to give the pure product 2-azetidinone (3a-k, 3n-o).
References
[1] Tetrahedron Letters, 1999, vol. 40, # 29, p. 5327 - 5330
[2] Tetrahedron, 1999, vol. 55, # 46, p. 13159 - 13170
[3] Tetrahedron Letters, 2010, vol. 51, # 1, p. 20 - 22
[4] Letters in Organic Chemistry, 2015, vol. 12, # 1, p. 44 - 49
[5] Tetrahedron Letters, 2002, vol. 43, # 18, p. 3323 - 3326
