Methyl Thioglycolate → 6-Bromo-benzo[b]thiophene-2-carboxylic acid methyl ester

Participants

Reaction Steps

In a similar manner to Example 9 Method A, 1-(benzo[b]thiophen-6-yl)propan-1-one was prepared starting from methyl thioglycolate (17.8 ml) and 4-bromo-2-fluorobenzaldehyde (40 g) which were reacted together to give methyl 6-bromobenzo[b]thiophene-2-carboxylate (55 g), m.p. 108-110° C. This ester was hydrolysed to give 6-bromobenzo[b]thiophene-2-carboxylic acid (48 g), which was decarboxylated using copper and quinoline at 180-200° C. for 2 hours to give 6-bromobenzo[b]thiophene (20.3 g), m.p. 53-55° C. This compound (7.5 g) was reacted with magnesium (0.9 g) and then with N-methoxy-N-methylpropionamide (6.1 g) to give 1-(benzo[b]thiophen-6-yl)propan-1-one (3.6 g) as a pale yellow solid which was used without further purification.

Provenance & Evidence