Efaroxan is an ñ<sub>2</sub>-adrenergic receptor antagonist and antagonist of the imidazoline receptor.
The Darzens reaction between 2-fluorobenzaldehyde (1) and ethyl 2-bromobutyrate (2) gives ethyl 2-ethyl-3-(2-fluorophenyl)oxirane-2-carboxylate (3). Catalytic hydrogenation over Pd/C gives ethyl 2-[(2-fluorophenyl)methyl]-2-hydroxybutanoate (4). Saponification of the ester then gives 2-[(2-fluorophenyl)methyl]-2-hydroxybutanoic acid (5). Treatment with 2 molar equivalents of sodium hydride apparently gives 2-ethyl-2,3-dihydrobenzofuran-2-carboxylic acid (6). Treatment of the carboxylic acid with thionyl chloride then gives the acid chloride and subsequent treatment of this with ethylenediamine in the presence of trimethylaluminium completed the synthesis of efaroxan (8).