合成路线1

An improved procedure, amenable to the industrial synthesis of the precursor (I) was further developed. Heck coupling of p-chloroiodobenzene (III) with allyl alcohol (IV) in the presence of tetramethylammonium chloride and a catalytic amount of palladium acetate provided 3-(p-chlorophenyl)propanal (V) along with minor amounts of its branched isomer (VI). Further reduction of this mixture with NaBH4 led to the respective alcohols (VII) and (VIII). Only the desired alcohol (VII) underwent bromination to the desired bromide (IX) in the presence of PBr3 in hot toluene, whereas the branched alcohol (VIII) was dehydrohalogenated to olefin (X). Subsequent alkylation of pyridazinedione (XI) with the above reaction mixture afforded the pure intermediate