Lithium dialkylcopper reaction

Lithium dialkylcopper reagents can be oxidized to symmetrical dimers by O2 at -78°C in THF. The reaction is successful for R = primary and secondary alkyl, vinylic, or aryl. Other oxidizing agents (e.g., nitrobenzene) can be used instead of O2. Vinylic copper reagents dimerize on treatment with oxygen, or simply on standing at 0°C for several days or at 25°C for several hours, to yield LS-dienes." ... 

Neither Grignard reagents nor lithium dialkylcopper reagents generally add to ordinary C=C double bonds. An exception is the reaction of (PhMe2Si)2 Cu(CN)Li to 8-oxabicyclo[3.2.1]oct-2-ene derivatives. Grignard reagents usually add only to double bonds susceptible to nucleophilic attack (e.g., fluoroalkenes and... 

Among other methods for the preparation of alkylated ketones are (1) the Stork enamine reaction (2-19), (2) the acetoacetic ester synthesis (0-94), (3) alkylation of (3-keto sulfones or sulfoxides (0-94), (4) acylation of CH3SOCH2 followed by reductive cleavage (0-109), (5) treatment of o-halo ketones with lithium dialkylcopper reagents (0-87), and (6) treatment of a-halo ketones with trialkylboranes (0-99). 

R = Me) or ( )-Ci8 (244 R = Et) juvenile hormone. The /5-oxidoylides may also be converted to chloro-olefins by halogenation. Reaction of lithium dialkylcopper complexes with acyclic allylic acetates proceeds by two predictable pathways depending on the nature of X, Y, and Z (Scheme 15). Thus the allylic acetate (245), on treatment with... 

The reaction of 4-(phenylsulfonyl)azetidin-2-one (128) with nucleophiles such as dialkylcopper lithium and Grignard reagents gives 4-alkyl, 4-allyl, 4-vinyl or 4-ethynyl-azetidinon-2-one (129) in good yields (equation 99)83. The yields of several azetidin-2-ones obtained by this method are given in Table 10. The reaction apparently proceeds through an intermediate azetin-2-one 131 derived from the five-membered coordination complex (equation 100). 

Monomeric, dialkylcopper complexes have been prepared and structurally characterized. The reaction of CpCuPPh3 with lithium fluorenyl18 provided the complex [(fluorenyl)2CuPPh3] [Li(THF)4]+ 11. The use of the anionic ligand CH(Me)PEt2NSiMe319 afforded the mononuclear complex 12 in which the ligand acts as a bridge... 

All these reactions involve addition of a dialkylcopper reagent [(CHsC C CH CuLi] to an alkyl halide. The dialkylcopper is prepared by treating 1-bromobutane with lithium, followed by addition of Cul ... 

This reaction can aiso be accompiished using dimethyicadmium on the acid chioride. FIGURE 19.26 Reactions of dialkylcopper lithium reagents with acyl halides. 

---