By condensation of 7-hydroxy-3,4-dimethylcoumarin (I) with 1-(3-chloropropyl)-4-(4-chlorobenzyl)piperazine (II) by means of K2CO3 and KI in refluxing butanone.
The total synthesis of picumast dihydrochloride has been described: The alkylation of piperazine (I) with 4-chlorobenzyl chloride (II) in ethanol gives 1-(4-chlorobenzyl)piperazine (III), which is alkylated again with 1-bromo-3-chloropropane (IV) by means of triethylamine in a suitable solvent to yield 1-(4-chlorobenzyl)-4-(3-chloropropyl)piperazine (V). Finally, this compound is condensed with 7-hydroxy-3,4-dimethylcoumarin (VI) by means of K2CO3 in refluxing butanone. Compound (VI) is obtained by cyclization of resorcinol (VII) with ethyl 2-methylacetoacetate (VIII) by means of refluxing acetic acid containing HCl.