No abstract

Reaction of aryl pyridyl ketones 1 with vinylmagnesium bromide followed by acetylation of the products 2 with acetic anhydride/EtgN and with 4-(dimethylamino)pyridine (DMAP) as a catalyst gave acetates 3 in high yields. Treatment of acetates 3 with dimethylamine in the presence of a palladium catalyst produced a mixture of E and Z isomers of 3-aryl-3-pyridylallylamines 4.

4-Chloroprenyl acetate (2), regioselectively prepared by palladium(II)-catalyzed 1,4-acetoxychlorination of isoprene, was selectively functionalized in the 1-and 4-positions to afford 6, which is readily transformed to the dimethyl ester of the pheromone (£,E)-3,7-dimethyldeca-2,6-diene-l,10-dioic acid (la) of the Monarch butterfly. The allylic chloro group in 2 was chemoselectively substituted with sodium dimethyl malonate (classically or with palladium(O) catalysis) without affecting the allylic acetoxy group, which subsequently was replaced with sodium methyl acetoacetate using palladium(0) catalysis to give 5. The configuration of the double bond in 5 is >95% E when triphenylphosphine is used as ligand. A double alkylation of 2 to 5 can also be performed as a one-pot sequence. Selective double decarboxylation of 5 gave methyl (£)-4-methyl-8-oxo-4-nonenoate (6) in 35% overall yield from isoprene. Transformation of 6 to the dimethyl ester of 1 has been described elsewhere.

266ChemInform Abstract tert.-Butyldimethylsilyl iodide (II), prepared in situ from the chloride (I), reacts with tetrahydrofuran (III) to give the 4-iodo-1-silyloxybutane (IV) which is converted to the derivatives (VI) by nucleophilic substitution reactions as outlined in the reaction scheme.

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