Reformatsky reaction
Reformatsky reaction | |
---|---|
Named after | Sergey Reformatsky |
Reaction type | Coupling reaction |
Identifiers | |
Organic Chemistry Portal | reformatsky-reaction |
RSC ontology ID | RXNO:0000036 |
The Reformatsky reaction (sometimes transliterated as Reformatskii reaction) is an organic reaction which condenses aldehydes or ketones with α-halo esters using metallic zinc to form β-hydroxy-esters:[1][2]
The
Some reviews have been published.[3][4]
In addition
Structure of the reagent
The crystal structures of the THF complexes of the Reformatsky reagents tert-butyl bromozincacetate[25] and ethyl bromozincacetate[26] have been determined. Both form cyclic eight-membered dimers in the solid state, but differ in stereochemistry: the eight-membered ring in the ethyl derivative adopts a tub-shaped conformation and has cis bromo groups and cis THF ligands, whereas in the tert-butyl derivative, the ring is in a chair form and the bromo groups and THF ligands are trans. Note that, in contrast to lithium and boron enolates, which have the metal(loid)s exclusively bond to oxygen, the zinc enolate moiety in the Reformatsky reagents have zinc atoms that are simultaneously O- and C-bound and can therefore be described as "organometallic".
ethyl bromozincacetate dimer | tert-butyl bromozincacetate dimer |
Reaction mechanism
Zinc metal is inserted into the carbon-halogen bond of the α-haloester by oxidative addition 1. This compound dimerizes and rearranges to form two zinc enolates 2. The oxygen on an aldehyde or ketone coordinates to the zinc to form the six-member chair like transition state 3. A rearrangement occurs in which zinc switches to the aldehyde or ketone oxygen and a carbon-carbon bond is formed 4. Acid workup 5,6 removes zinc to yield zinc(II) salts and a β-hydroxy-ester 7.[5]
Variations
In one variation of the Reformatsky reaction[27] an iodolactam is coupled with an aldehyde with triethylborane in toluene at -78 °C.
See also
- Aldol reaction
- Blaise reaction
- Claisen condensation
- Example use in total synthesis: Mukaiyama Taxol total synthesis (B ring construction)
References
- .
- ^ Reformatsky, S. (1890). "Action of zinc and ethyl chloroacetate on ketones and aldehydes". J. Russ. Phys. Chem. Soc. 22: 44.
- ISBN 9780471264187.
- ISBN 0471264180.
- ^ a b c d Kurti, L.; Czako, B. Strategic Applications of Named Reactions in Organic Synthesis; Elsevier: Burlington, 2005.
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- S2CID 197541600.
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- .
- PMID 11672062.
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- PMID 14973617.
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- .
- .
- PMID 14507186.
- .
- .
- ^ PMID 16402826.