Sulfuryl chloride → 4-(methoxycarbonyl)-2-methylthiophen-3-aminium chloride

Participants

Reaction Conditions

Reaction Steps

80.7 g of methyl 4-amino-5-methyl-2,5-dihydrothiophene-3-carboxylate (2) (338 mmol, content: 72.6%) were dissolved in 88 ml of chlorobenzene and cooled to −10° C. A solution of 50.2 g of sulfuryl chloride (372 mmol) in 59 ml of chlorobenzene in the temperature range of −10-0° C. was added dropwise to this solution over a period of 1 h. The reaction mixture was subsequently stirred at −10-0° C. for another 1 h and then warmed to room temperature. For workup, the reaction mixture was concentrated under reduced pressure. 95 g of methyl 4-amino-5-methylthiophene-3-carboxylate hydrochloride (5) were obtained (96% of theory, content: 58.7%, determined as the free amine). The product was characterized after release of the amine with NaHCO3 solution (m.p.: 65° C.; 1H NMR (400 MHz, d3-DMSO): 2.62 (s), 4.25 (s), 5.18 (bs), 8.22 (s)).

Provenance & Evidence