Sodium Carbonate → HCID 87070217, compound

Participants

Reaction Conditions

Reaction Steps

A flask containing a mixture of methyl 3-amino-2,6-dibromoisonicotinate (3.00 g, 9.68 mmol), 2-benzyloxybenzeneboronic acid (2.52 g, 11.1 mmol), tetrakistriphenylphosphine palladium (0) (0.533 g, 0.461 mmol) and Na2CO3 (2.64 g, 24.9 mmol) was flushed with nitrogen. Toluene (24 mL) and methanol (8 mL) were added and the reaction was heated at 110° C. for 23 h. This was partitioned between EtOAc and aq. sat. sodium bicarbonate solution. The organic phase was washed with sat. aq. sodium bicarbonate solution and brine and then dried with sodium sulfate. Removal of the solvent followed by silica gel chromatography (step gradient elution with hexane containing 0 to 15% EtOAc afforded methyl 3-amino-2-(2-(benzyloxy)phenyl)-6-bromoisonicotinate (2.80 gm, 6.78 mmol, 74% yield) as a solid. This was quickly dissolved in TFA (40 mL) and the yellow solution cooled in an ice-bath. Sodium nitrite (0.935 g, 13.6 mmol) was added with stirring to give a dark red mixture. After 30 min, solid sodium azide (4.40 g, 67.8 mmol) was added over 5 min followed by Et2O (40 mL). This was stirred in the ice-bath for 30 min and then partitioned between H2O and EtOAc. The organic phase was separated and most of the solvent was removed. The residue was diluted with EtOAc, washed with aq. sat. NaHCO3 solution and brine and then dried over sodium sulfate. The solution was concentrated to about 50 ml volume and the solid was with EtOAc, to leave methyl 3-azido-2-(2-(benzyloxy)phenyl)-6-bromoisonicotinate (2.70 gm, 4.39 mmol, 65% yield) as a solid. 1,2-Dichloroethane (3 mL), rhodium octanoate dimer (0.171 g, 0.220 mmol), and crushed 4A° molecular sieves (2.70 g) were added and the mixture was heated at 80° C. for 48 h. It was diluted with a mixture of 25% MeOH in DCM and filtered. The solid was washed with additional 25% MeOH in DCM and the solvents removed from the combined filtrates. The residue was suspended in MeOH and filtration followed by washing with MeOH left methyl 9-(benzyloxy)-2-bromo-5H-pyrido[3,2-b]indole-4-carboxylate (1.84 g, 97% yield) as a solid. MS (ESI) m/z 411.0 (M+H). 1H NMR (500 MHz, chloroform-d) d ppm 9.63 (1H, br. s.), 7.98 (1H, s), 7.77 (2H, d, J=7.32 Hz), 7.48 (3H, m), 7.34 (1H, m), 7.16 (1H, d, J=7.93 Hz), 6.85 (1H, d, J=7.93 Hz), 5.48 (2H, s), 4.09 (3H, s).

Provenance & Evidence