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Enones provide a solution to regioselectivity problems

المؤلف:  Jonathan Clayden , Nick Greeves , Stuart Warren

المصدر:  ORGANIC CHEMISTRY

الجزء والصفحة:  ص601-602

2025-06-28

674

Enolates can be made regiospecific cally from, for example, silyl enol ethers or enol acetates just by treating them with an alkyllithium. These are both substitution reactions in which RLi displaces the enolate: one is SN2(Si) and the other is attack at C=O. Provided there is no proton source, the enolate products have the same regiochemistry as their stable precursors, and single enolate regioisomers are formed.

But there is a problem: forming enol ethers or enol esters will usually itself require a regio selective enolization! There are two situations in which this method is nonetheless useful: when the more substituted lithium enolate (which is hard to make selectively otherwise) is required, and when a silyl enol ether can be formed by a method not involving deprotonation. These methods are what we shall now consider.