合成路线1

Several novel syntheses of 2-butyl-5-chloro-3H-imidazole-4-carbaldehyde (XI), a key intermediate in the synthesis of losartan, have been described: 1) Treatment of glycine methyl ester hydrochloride (I) with NaOH in methanol, followed by reaction with methyl pentanimidate (II), gives 2-butyl-4,5-dihydro-1H-imidazol-5-one (III), which is treated with POCl3 to give the 2-butyl-5-chloro-1H-imidazole (IV). Reaction of (IV) with POCl3 and DMF yields the enamine (V), which is finally hydrolyzed with water to 2-butyl-5-chloro-3H-imidazole-4-carbaldehyde (XI), the desired intemediate in the synthesis of losartan. 2) Imidazolinone (III) can also be obtained by cyclization of chloroacetic acid methyl ester (VI), chloroacetyl chloride (VII) or bromoacetyl bromide (VIII) with pentanamidine (IX) by means of NaOH in methanol. 3) Alternatively, imidazolinone (III) can be treated with dimethylformamide dimethylacetal in dichloromethane yielding the enamine (X), which is finally treated with POCl3 and hydrolyzed with water. 4) The reaction of glycine (XI) with methyl pentanimidate (II) in NaOH/MeOH gives amidine (XII), which, without isolation, is treated with POCl3 and DMF at 100 C for 2 h, and then hydrolyzed with water to give the desired 2-butyl-5-chloro-3H-imidazole-4-carbaldehyde. Methyl pentanimidate (II) is obtained treating a solution of valeronitrile in MeOH with HCl gas followed by neutralization with aqueous KOH and extraction with Et2O.