Oxalyl chloride → Tert-butyl 2-(5-bromobenzo[d]oxazole-2-carboxamido)-4-(4-chlorophenyl)thiophene-3-carboxylate

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Reaction Steps

To a suspension of 5-bromobenzo[d]oxazole-2-carboxylic acid (2A, 60 mg, 0.25 mmol) in DCM (5 ml) at room temperature was added oxalyl chloride (0.2 ml) and catalytic amount of DMF. The mixture was stirred at room temperature for 17 hours. The solvent was removed under vacuum to dryness. The residue was dissolved in DCM (5 ml) followed be addition of tert-butyl 2-amino-4-(4-chlorophenyl)thiophene-3-carboxylate (1A, 62 mg, 0.2 mmol) and DIEA (0.3 ml). The mixture was stirred at room temperature for 17 hours. The reaction mixture was diluted with DCM (5 ml) washed with 1N aqueous HCl (3×5 ml), water (1×5 ml), 1N aqueous NaOH (3×5 ml) and dried over anhydrous sodium sulfate. The drying agent was removed by filtration. The filtrate was concentrated under vacuum to give analytically pure 3A which was used in the next step without further purification. LC-MS: calcd. for C23H18BrClN2O4S: 532 (M+1); found: 532.

Provenance & Evidence