The chlorination of 5-(hydroxymethyl)imidazo[1,2-a]pyridine (I) with SOCl2 in dichloromethane gives the corresponding chloromethyl derivative (II), which is condensed with 1,4-diaminobutane (III) in refluxing acetonitrile to yield 5-(4-aminobutylaminomethyl)imidazo[1,2-a]pyridine (IV). The sulfonation of (IV) with N-phenyltrifluoromethylsulfonimide (V) and TEA in acetonitrile affords the sulfonamide (VI), which is protected with Boc2O in ethanol to provide the carbamate (VII). The acylation of (VII) with trichloroacetyl chloride and DMAP in refluxing chloroform gives the 3-trichloroacetyl derivative (VIII), which is finally cyclized by means of Tms-I and NaHCO3 in chloroform.
The reaction of ethyl chloroacetate (I) with ethyl formate (II) by means of potassium tert-butoxide in diisopropyl ether gives the 2-formylchloroacetate (III), which is cyclized with 6-methylpyridine-2-amine (IV) by means of conc. H2SO4, yielding 5-methylimidazo[1,2-a]pyridine-3-carboxylic acid ethyl ester (V). The chlorination of (V) with NCS in THF affords the chloromethyl derivative (VI), which is condensed with the monoprotected diamine (VII) by means of TEA to provide the adduct (VIII). The cyclization of (VIII) by means of NaOMe, TEA and NaI in DMF gives 4-[4-(benzyloxycarbonylamino)butyl]-4,5-dihydro-3H-1,4,8b-triazaacenaphthylen-3-one (IX), which is deprotected with H2 over Pd/C in MeOH, yielding the butylamine derivative (X). Finally, this compound is sulfonated with N-phenyltrifluoromethylsulfonimide (XI) and TEA in DMF.