N-methoxy-N-methyl-1,4-dioxane-2-carboxamide

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 6-Bromo-1,4-dimethylindoline-2,3-dione and 4-bromo-1,6-dimethylindoline-2,3-dione. A solution of 1,4-diazabicyclo[2.2.2]octane (DABCO) (1.912 g, 17.05 mmol) in chloroform (5 mL) was cooled down to 0° C. under nitrogen gas and oxalyl chloride (1.492 mL, 17.05 mmol) was added dropwise, to form a pale yellow solid. To this solid was added slowly 3-bromo-N,N,5-trimethylaniline (0.73 g, 3.41 mmol) in chloroform (3 mL) at 0° C. The reaction mixture changed from a yellow suspension to a brown suspension. The reaction mixture was then warmed to room temperature, transferred into a sealed tube and heated to 90° C. for 3 h. The reaction mixture was neutralized with 10% sodium hydroxide solution to pH 8-9. The water layer was extracted with ethyl acetate (3×100 mL), washed with saturated ammonium chloride and brine, dried over magnesium sulfate, filtered and concentrated down to give the mixture of regioisomers as a red-brown solid. The regioisomers were separated by column chromatography (eluting with 0-100% ethyl acetate in hexane). The least polar compound was identified as 6-bromo-1,4-dimethylindoline-2,3-dione (0.34 g, 39.2%). 1H NMR (400 MHz, DMSO-d6) δ (ppm) 7.27 (s, 1H), 7.21 (s, 1H), 3.12 (s, 3H), 2.44 (s, 3H). MS (ESI) m/z 256.1 [M+2]+. The regiochemistry was confirmed by NOE (NOE-NMR (400 MHz, DMSO-d6) δ (ppm) 2.44 (irradiated peak suppressed one major peak at 7.21 ppm). The most polar compound spot was identified as 4-bromo-1,6-dimethylindoline-2,3-dione and was further purified by trituration with methanol (0.146 g, 17%). 1H NMR (400 MHz, DMSO-d6) δ (ppm) 7.16 (s, 1H), 7.02 (s, 1H), 3.11 (s, 3H), 2.38 (s, 3H). MS (ESI) m/z 256.1 [M+2]+. The regiochemistry was confirmed by nOE (NOE-NMR (400 MHz, DMSO-d6) δ (ppm) 2.38 (irradiated peak suppressed two major peaks at 7.02 and 7.16 ppm). to form a pale yellow solid transferred into a sealed tube heated to 90° C. for 3 h The water layer was extracted with ethyl acetate (3×100 mL) washed with saturated ammonium chloride and brine dried over magnesium sulfate filtered concentrated down to give the mixture of regioisomers as a red-brown solid The regioisomers were separated by column chromatography (eluting with 0-100% ethyl acetate in hexane) was further purified by trituration with methanol (0.146 g, 17%)