ChemInform Abstract: Preparation of Ketones from Esters via Substituted Cyclopropanols. Application to the Synthesis of (.+-.)-Ipsenol, (.+-.)-Ipsdienol and Amitinol, the Components of Aggregation Pheromones of the Ips Bark Beetles.
Abstract
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ChemInform Abstract
Key step in the synthesis of title pheromones (.+-.)-ipsenol (Xa), (.+-.)-ipsdienol (Xb), and amitinol (IX) is the preparation of methyl ketone (IV) starting from an ester. Titanium-promoted addition of ethyl acetate to the double bond of vinylacetic aldehyde acetal (I) provides a cyclopropanol derivative (III), which is regioselectively opened by a bromination—dehydrobromination sequence. Reduction of the ketone, chlorination, and dehydrochlorination reactions then afford diene acetal (V) as key intermediate, which provides the title pheromones by reaction with the suitable Grignard reagents or by Wittig olefination.