Dibutyltin dichloride → 5-Bromo-3-(1,4-dioxa-spiro[4.5]dec-8-ylamino)-thiophene-2-carboxylic acid methyl ester

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Reaktionsschritte

A suspension of 3-Amino-5-bromo-thiophene-2-carboxylic acid methyl ester (1.03 g, 4.38 mmol) in dry THF (1.1 ml) was treated with 1,4-cyclohexanedione monoethylene ketal (684 mg, 4.38 mmol), followed by dibutyltin dichloride (133 mg, 0.44 mmol). After 5 min, phenyl silane (877 μL, 4.8 mmol) was added and the reaction mixture was stirred at room temperature for 2 days when a clear solution resulted. The solution was then concentrated and the residue purified by silica gel column chromatography using EtOAc:hexanes as eluent to furnished 5-Bromo-3-(1,4-dioxa-spiro[4.5]dec-8-ylamino)-thiophene-2-carboxylic acid methyl ester (1.11 g, 68% yield). 1H NMR (CDCl3, 400 MHz): 6.90 (br s, 1H), 6.65 (s, 1H), 3.95 (s, 4H), 3.78 (s, 3H), 3.35 (m, 1H), 2.00 (m, 2H), 1.80 (m, 2H), 1.65 (m, 4H).

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