Methanol → 8-Bromo-4,5-dihydrobenzo[2,3]oxepino[4,5-d]thiazole-2-carboxylic acid

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Reaction Steps

A mixture of 8-bromo-4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulene-2-carboxylic acid ethyl ester (3.32 g, 9.38 mmol), MeOH (75 mL) and water (50 mL) was treated with sodium hydroxide (562 mg, 14.06 mmol) at RT. After 90 minutes THF (20 mL) was added to aid dissolution. After 60 minutes the mixture was concentrated in vacuo, dissolved in water (200 mL) and carefully acidified to pH1 with 2N HCl. The resulting solid was collected by filtration, washed with water and dried under vacuum to afford 8-bromo-4,5-dihydro-6-oxa-3-thia-1-aza-benzo[e]azulene-2-carboxylic acid (1.86 g, 61%). LCMS RT=4.91 min, no [M+H]+=326/328

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