Ammonia → methyl 1-methyl-1H-indole-2-carboxylate

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Reaction Steps

A stirred suspension of methyl 1H-indole-2-carboxylate (5.0 g), dimethyl sulphate (9 ml) and potassium carbonate (10.4 g) in dry acetone (200 ml) was heated under reflux for 24 h. After cooling to room temperature 5% ammonia solution (50 ml) was added and the mixture stirred for 2 hours. The solvent was removed in vacuo and the residue partitioned between dichloromethane and water. The organic layer was dried and the solvent evaporated to give methyl 1-methyl-1H-indole-2-carboxylate (5.4 g) as a white solid; IR (CHBr3) max 1695 cm-1. The ester was treated with ethylenediamine and trimethylaluminium as described in Example 1(a). Purification via column chromatography on silica eluting with 5% v/v methanolic ammonia in dichloromethane gave 2-(2-imidazolin-2-yl)-1-methyl-1H-indole as a white solid. The hydrochloride salt was prepared as in Example 3 and that recrystallised from ethanol/diethyl ether; mp 290°-295° C. (decomp) (Literature mp 260°-280° C. (decomp) D. J. Hlasta, D. Luttinger, M. H. Perrone, M. J. Silbernagel, S. J. Ward and D. R. Haubrich, J. Med. Chem. 1967, 30, 1555).

Provenance & Evidence