Normant cuprates

Kant and coworkers [89] synthesized cefzil (2-167) through a Normant cuprate addition to allene 2-164, readily available from inexpensive penicillins, to give 2-165, which cyclized to the cefzil precursor 2-166 in a SN -type reaction (Scheme 2.38). The conversion of 2-166 into 2-167 was already known [90]. 

There is a serious limitation with respect to the structure of ketones that are accessible by 1,4-addition of Gilman or Normant cuprates to a,/l-unsaturated ketones. As a... 

The further transformations of the enolate C start with a reductive elimination (additional examples of this type of reaction can be found in Chapter 13), which gives the enolate D. This compound is not a normal lithium enolate because it is associated with one equivalent of CuR. The CuR-containing enolate D remains inert until the aqueous workup. As you can see from Figure 8.35, 50% of the groups R contained in the Gilman cuprate are lost through formation of the stoichiometric by-product CuR. This disadvantage does not occur in the 1,4-additions of Normant and Knochel cuprates. 

J. Villieras, A. Reliquet, and J. F. Normant,/. Organometallic Chem., 1978,144,17. Formation of cuprates from carbenoids and RCu. 

Hydrozirconation of alkynes, followed by halogenation with N-halosuccinimide (N-bromo, IV-chloro) affords vinyl halides in reasonable yields (Hart et al, 1975). Vinyl cuprates, obtained by stereospecific addition of alkylcoppers to terminal alkynes, react with iodine in ether at —30° to give vinyl iodides (Normant et al, 1974). 

A. Alexakis, G. Cahiez, and J. F. Normant, Tetrahedron, 1980, 36, 1961. (Z)-Alkenyl cuprate reactions with various electrophiles, e.g., CO2, epoxides, aldehydes, ot,jS-enones, and alkynes. 

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