Synthesis
GENERAL METHOD: Salicylaldehyde (10 mmol) was mixed with urea nitrate (10 mmol) in acetonitrile-water solvent mixture (95:5, 5 ml, v/v) in a 25 ml round bottom flask. The reaction mixture was placed in a Milestone Start SYNTH microwave reactor and heated at 80°C for 40-50 min. Upon completion of the reaction, the reaction mixture was cooled to room temperature, quenched with water and extracted with dichloromethane. The organic phase was concentrated under reduced pressure and the residue was purified by silica gel column chromatography to afford the target product 3-nitrosalicylaldehyde. In all experiments, o-nitrosalicylaldehyde was selectively generated and no para-nitro-substituted by-products were detected. The resulting compounds were characterized by 1H NMR, 13C NMR, melting point determination (for solid samples), GC-MS analysis and comparison with standards.
References
[1] Chinese Chemical Letters, 2010, vol. 21, # 4, p. 403 - 406
[2] Synthetic Communications, 2011, vol. 41, # 20, p. 2985 - 2992
[3] Tetrahedron Letters, 2014, vol. 55, # 7, p. 1320 - 1322
[4] Patent: WO2012/92880, 2012, A1. Location in patent: Page/Page column 57-58
[5] Tetrahedron, 1969, vol. 25, p. 3251 - 3266
