Zinc versus Samarium Mediated Reformatsky Reactions

4 Zinc versus Samarium Mediated Reformatsky Reactions 

According to a general definition, the Reformatsky reaction can be taken as subsuming all enolate formations by oxidative addition of a metal or a low-valent metal salt into a carbon-halogen bond activated by a vicinal carbonyl group, followed by reaction of the enolates thus formed with an appropriate electrophile [23]. The insertion of metallic zinc into a-halo esters is historically the first and still the most widely used form of this process although Zn may be beneficially replaced but other metals and reducing metal salts in certain cases. 

A particular advantage of the Reformatsky reaction stems from the fact that the site of reaction is strictly determined by the halogen moiety. This feature can be advantageously used for regioselective enolate formations in polycarbonyl compounds which are difficult to achieve by proton abstraction methods. As a consequence, this transformation has seen a renaissance over recent decades and has found many elegant uses, particularly in intramolecular variants [23]. 

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