Alpha-Methylstyrene → Ethyl 2-amino-1-benzothiophene-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

14.4 g of hydrogenation catalyst (Degussa-Hüls; E 101 R/W 5%) are added to a solution of 36 g of ethyl 2-acetylaminotetrahydrobenzothiophene-3-carboxylate in 250 ml of xylene (isomeric mixture) and the mixture is heated to a constant temperature of 139° C. to 141° C. 47 g of α-methylstyrene are metered in over a period of 5 h. The mixture is then refluxed for a further 36 h. It is cooled to 102° C., 32 g of pyrrolidine are added and the mixture is brought back to the reflux point (127° C.); it is stirred for 20 h at this temperature. After cooling to 20° C., the Pd/carbon is filtered off, the filtrate is concentrated to a residue, and the residue is taken up in 75 ml of ethyl acetate and washed with three times 12 ml of 10% hydrochloric acid. The organic phase is washed with twice 5 ml of water and then concentrated to a residue. This is recrystallized from 50 ml of isopropanol to give 21 g of ethyl 2-aminobenzothiophene-3-carboxylate in the form of slightly yellowish crystals (70.5% yield).

Provenance & Evidence