Mixed copper-zinc reagent

Mixed copper-zinc reagents also react with alkynes to give alkenylcopper species that can undergo subsequent electrophilic substitution. 

Scheme 8.3. Conjugate Addition and Alkylation Reactions of Mixed Copper-Zinc Reagents...

The addition of methylzinc (and cadmium) organometallics to chiral aldehydes proceeds with low stereoselectivity and leads to a mixture of syn- and anti-alcohols (see Scheme 22). A better dia-stereoselectivity can be achieved by using the mixed copper-zinc reagents RCu(CN)ZnI. ° In contrast, the more reactive diallylzinc reacts with several a-alkoxy aldehydes of type (43) to give anti addition... 

In one recent synthesis, 91 was prepared using a photoreductive cyclization of a N,N-unsaturated dialkyl-2-oxocyclopentanecarboxamide [274]. In another synthesis of 91, a mixed copper, zinc organometallic reagent was added to a 2,5-disubstituted V-acylpyridinium salt to... 

In the presence of a Lewis acid, alkyl zinc halides react with aromatic aldehydes to give secondary alcohols. However, alkyl zinc reagents are less reactive than their allyl derivatives and reaction with aliphatic aldehydes is very sluggish. A solution to this is the use (in the presence of aLewis acid) of either the dialkyl zinc reagent or the mixed copper-zinc species RCu(CN)ZnX, formed by transmetaUation of the alkyl... 

A mixed copper and zinc reagent (prepared in three steps from an o-toluidine via the benzyl bromide) reacts with various electrophilic reagents such as acyl... 

A proper choice of the catalyst allows the extension of the coupling to aryl iodides.107 Yields are satisfactory with para substituted electrophiles, less convenient with the ortho isomers. Further extension was obtained by replacing the palladium catalyst by copper cyanide, and the coupling reaction proceeds without sonication. The copper-zinc mixed reagent is able to couple with allylic... 

Replacing the palladium catalyst by copper cyanide gives a copper-zinc mixed reagent,i72 able to couple with allylic and propargylic halides. Modified amino acid derivatives were thus obtained. 

---