Palladium-Catalyzed Reaction of 1,3-Diene Monoepoxides with β-Keto Acids. Allylic Alkylation and Isomerization of 1,3-Diene Monoepoxides

Article abstract of DOI:10.1021/jo00376a031

Tetrakis(triphenylphosphine)palladium catalyzed the decarboxylative allylic alkylation of 1,3-diene monoepoxides with β-keto acids at ambient temperature to produce keto allylic alcohols in moderate to good yields. 1,3-Diene monoepoxides employed in this reaction were 3,4-epoxy-4-methyl-1-butene (2), 3,4-epoxy-2-methyl-1-butene (3), 4,5-epoxy-2-hexene (4), and 3,4-epoxy-1-pentene (5).As β-keto acids, 1-oxocyclohexane-2-carboxylic acid, benzoylacetic acid (1), and 1,3-acetonedicarboxylic acid were used.The allylic alkylation of 1,3-diene monoepoxide took place regioselectively at the allylic carbon atom distal the hydroxyl group .The stereochemistry of the resultant carbon-carbon double bond was predominantly to exclusively E.On the contrary, 3,4-epoxy-2,3-dimethyl-1-butene (6), 4,5-epoxy-2,5-dimethyl-2-hexene (7), and 3,4-epoxy-1-cyclohexene (8) took a different course of the reaction to undergo the palladium-catalyzed isomerization.The isomerization of 6 and 7 was accelerated by 1, but that of 8 was not.The effect of the structure of 1,3-diene monoepoxides upon the reaction course and the role of β-keto acid in the isomerization were discussed.