Abstract
Addition of carboxylic acid dianions appears to be a potential alternative to the use of aluminium enolates for nucleophilic ring opening of epoxides. These conditions require the use of a sub-stoichiometric amount of amine (10% mol) for dianion generation and the previous activation of the epoxide with LiCl. Yields are good, with high regioselectivity, but the use of styrene oxide led, unexpectedly, to a mixture resulting from the attack on both the primary and secondary carbon atoms. Generally, a low diastereoselectivity is seen on attack at the primary center, however only one diastereoisomer was obtained from attack to the secondary carbon of the styrene oxide.
Highlights
Addition of carboxylic acid dianions appears to be a potential alternative to the use of aluminium enolates for nucleophilic ring opening of epoxides
A low diastereoselectivity is seen on attack at the primary center, only one diastereoisomer was obtained from attack to the secondary carbon of the styrene oxide
Better results can generally only be attained by using the corresponding aluminium ester or lithium amide enolates. γ-Hydroxycarboxylic acids derivatives are rarely accessed via epoxide ring opening of lithium enolates [4] and some alternative routes have been proposed [5]
Summary
Abstract: Addition of carboxylic acid dianions appears to be a potential alternative to the use of aluminium enolates for nucleophilic ring opening of epoxides. These conditions require the use of a sub-stoichiometric amount of amine (10% mol) for dianion generation and the previous activation of the epoxide with LiCl. Yields are good, with high regioselectivity, but the use of styrene oxide led, unexpectedly, to a mixture resulting from the attack on both the primary and secondary carbon atoms. Our group has developed efficient conditions for the addition of lithium dianions of carboxylic acids to epoxides as an alternative route to aluminium enolate chemistry.
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