Copper Reformatsky reactions

Reformatski reaction Aldehydes and ketones react with a-bromo- fatty acid esters in the presence of zinc powder to give -hydroxy-esters which may be dehydrated to give a-, 0-unsaturated esters. a-Chloroesters will react if copper powder is used in conjunction with the zinc. 

Several techniques have been used to activate the zinc metal and improve yields. For example, pretreatment of zinc dust with a solution of copper acetate gives a more reactive zinc-copper couple.130 Exposure to trimethylsilyl chloride also activates the zinc.131 Scheme 7.5 gives some examples of the Reformatsky reaction. 

Reformatsky reaction. The Reformatsky reaction of ethyl bromoacetate with several aldehydes and ketones proceeds in improved yields when the zinc is replaced by Le Goff s zinc-copper couple (1, 1020). THF is usually superior to ether as solvent. ... 

The Reformatsky reagents are the compounds of a a-haloester with zinc. Further, with the compounds of /(- or y-haloester with zinc the coupling reactions are able to proceed in the presence of catalysts such as palladium, copper and nickel compounds. These reactions are called the Remote Reformatsky reactions. For example, the reaction with palladium catalyst is shown in eq. (5.24) [42],... 

Further protocols for the enantioselective Reformatsky reaction were reported using different additives [167] and copper [168] and nickel salts the latter... 

Intramolecular Reformatsky-type reactions a-methylene-t-lactones. Reaction of the (Z)-bromoaldehyde (1) in a dilute solution of THF with zinc dust at 65° or with zinc-copper couple at 25 leads to the c/i -fused a-methylene-y-lactone (2) in 60-62% yields. The reaction involves an intramolecular Reformatsky-type reaction followed by spontaneous lactonization. The same product (2) is also obtained from the (E)-isomer of (1) in 46% yield together with the transfused isomer of (2). The reaction of (1) with bis(l,5-cyclooctadicnc)nickel (4, 33-35 5, 34-35) also yields (2) in 527 yield. It is obtained in comparable yield... 

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