Potassium bisulfate → methyl 3-[(E)-tert-butylsulfinyliminomethyl]-5,6,7,8-tetrahydroindolizine-2-carboxylate

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Reaction Steps

A 500-mL single-neck round-bottomed flask equipped with a magnetic stirrer was charged with methyl 3-formyl-5,6,7,8-tetrahydroindolizine-2-carboxylate (10.0 g, 48.3 mmol, 1.0 eq.), 2-methylpropane-2-sulfinamide (11.7 g, 96.6 mmol, 2.0 eq.), KHSO4 (32.8 g, 241.5 mmol, 5 eq.), and dichloromethane (250 mL). The mixture was stirred at room temperature for 10 h. It was then filtered and filtrate was concentrated under reduced pressure. The resulting residue was purified by silica-gel column chromatography eluting with 1:3 ethyl acetate/petroleum ether to afford 238a (12.4 g, 83%) as a yellow solid. MS: [M+H]+ 311.3.

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