合成路线1

The condensation of 2-hydroxybenzaldehyde (I) with ethyl 2-bromobutyrate (II) by means of K2CO3 and NaI in DMF gives ethyl-2-(2-formylphenoxy) butyrate (III), which is reduced with NaBH4 and NaOEt in ethanol yielding the hydroxymethyl derivative (IV). The reaction of (IV) with SOCl2 affords the corresponding chloromethyl compound (V), which is cyclized by means of NaH in N-methylpyrrolidone to give 2-ethyl-2,3-dihydrobenzofuran-2-carboxylic acid ethyl ester (VI). The hydrolysis of the ethyl ester of (VI) with NaOH in methanol yields the expected carboxylic acid (VII), which is treated with SOCl2 and then with NH3 to afford the amide (VIII). This compound can also be obtained directly from ester (VI) by reaction with NH3. The dehydration of (VIII) by means of P2O5 or POCl3 gives the nitrile (IX), which is treated with HCl in ethanol yielding the carboxyimidate (X). Finally, this compound is cyclized with ethylenediamine (XI) in ethanol.