Triethylamine → 3-pyridyl-N-t-butyl nitrone

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

According to a protocol of A. Dondoni, et al., (Synth. Commun. 1994, 24, 2537-2550), an ovendried 250 mL round-bottomed flask equipped with a magnetic stir bar, reflux condenser and adapter to an argon line was charged with 2.512 g (20.0 mmol) of N-tert-butylhydroxylamine hydrochloride (1), 2.144 g (20.0 mmol) of pyridine-3-carboxaldehyde (2b), and 2.889 g (22.0 mmol) of MgSO4.100 mL of anhydrous toluene were added followed by 2.024 g (20.0 mmol, 2.79 mL) of anhydrous Et3N. The reaction mixture was heated to 100-110° C. under atmosphere of argon, and the reaction course was followed by t.l.c. and GC/MS. After 3-5 h, the reaction was cooled to room temperature, MgSO4 was filtered off, and the solvent was evaporated under reduced pressure to yield a dark yellow-green mixture of product and Et3N HCl. The solids were dissolved in EtOAc and the solution was subsequently washed with a saturated aq. NaHCO3-solution (50 mL) to remove Et3N HCl, water (50 mL), and brine (50 mL), dried over MgSO4, filtered, and evaporated under reduced pressure. The crude product was purified by passing through a short plug of silica gel (EtOAc/hexanes (1: 1) to yield after evaporation 3.000 g (84%) of a pale yellow solid. Rf: 0.61 (EtOAc/hexanes=1:9, UV254-quenching). GC: Rt: 3.92 min. 1H NMR (300 MHz, CDCl3, room temp.): δ9.06 (dt, J=8.4,1.8 Hz, 1H, Ar-H), 8.93 (d, J=1.8 Hz, 1H, Ar-H), 8.53 (dd, J=8.8, 1.8 Hz, 1H, Ar-H), 7.56 (s, 1H, HC(═N)), 7.31 (dd, J=8.1, 4.8 Hz, 1H, Ar- H), 1.54 (s, 9H, C(CH3)3) ppm. 13C NMR (75 MHz, CDCl3, room temp.): δ150.20, 150.09, 134.57, 127.49, 126.91, 123.40, 71.43, 28.24 ppm. MS: m/z=178 (M+), 147, 122 (b.p., M+—H2C═C(CH3)2), 106, 79, 57.

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