Lesopitron dihydrochloride was obtained following two related procedures. 1) Reaction of 4-chloropyrazole (I) with 1,4-dibromobutane (II) gives 1-(4-bromobutyl)-4-chloropyrazole (III). Compound (III) is refluxed with 2-(1-piperazinyl)pyrimidine (IV) and potassium carbonate in DMF to give lesopitron (V), which is treated with isopropyl alcohol saturated with hydrochloric acid to pH 4.5-5 . 2) 2-(1-Piperazinyl)pyrimidine (IV) reacts with 1,4-dibromobutane (II) to yield 8-(2-pyrimidinyl)-8-aza-5-azoniaspiro[4.5]decane bromide (VI). The quaternary salt (VI) undergoes reaction with 4-chloropyrazole (I) in DMF in the presence of potassium carbonate to afford the free base.

Lesopitron dihydrochloride was obtained following two related procedures. 1) Reaction of 4-chloropyrazole (I) with 1,4-dibromobutane (II) gives 1-(4-bromobutyl)-4-chloropyrazole (III). Compound (III) is refluxed with 2-(1-piperazinyl)pyrimidine (IV) and potassium carbonate in DMF to give lesopitron (V), which is treated with isopropyl alcohol saturated with hydrochloric acid to pH 4.5-5 . 2) 2-(1-Piperazinyl)pyrimidine (IV) reacts with 1,4-dibromobutane (II) to yield 8-(2-pyrimidinyl)-8-aza-5-azoniaspiro[4.5]decane bromide (VI). The quaternary salt (VI) undergoes reaction with 4-chloropyrazole (I) in DMF in the presence of potassium carbonate to afford the free base.