Coupling reactions Organocopper reagents

Halodiazinones undergo palladium-catalysed couplings with boronic acids and stannanes, but the reactions appear to be less consistent than with other systems. Temporary protection as silyl derivatives," or the use of additives such as silver oxide are beneficial in some cases, but it is often preferable to carry out transformations on alkoxydiazines, followed by hydrolysis. Direct coupling with organocopper reagents has also been described." ... 

One example for the reaction of a 229-type copper reagent is shown in Equation (128). Neopentyl-substituted organocopper reagent 230, which bears aldehyde, is generated followed by treatment with acetyl chloride to provide coupling product 231 in 70% yield. Application of this method to the selective functionalization of polyhalogenated aromatics was also reported.497... 

Buynak et al. reported the synthesis of representative 7-vinylidenecephalosporine derivatives bearing an axial allene chirality (Scheme 4.5) [9]. A chiral allene 24 was prepared stereoselectively utilizing the reaction of an organocopper reagent with propargyl triflate 23, obtained by a diastereoselective ethynylation of the ketone 22 with ethynylmagnesium bromide. Terminally unsubstituted allene 26 was synthesized via bromination of the triflate 23 followed by reduction of the bromide 25 with a zinc-copper couple. 

Sn2 substitution using organocopper reagents is an efficient method for the synthesis of 3-substituted olefins. In the synthesis of farnesyl diphosphate analogues (43, 45) as potential inhibitors of the enzyme protein-farnesyl transferase, for example, organocopper methodology was compared with the Stifle reaction [33] and the Suzuki reaction [34], frequently used in the coupling of vinyl triflates with... 

Scheme 57 illustrates an example of this process coupling of the lithio reagent derived from vinyl stannane 237 with epoxide 242 leads to the C-disaccharide derivative 243 in good yield. A double transmetallation to give an organocopper reagent 244 can facilitate the C-glycosylation reaction with allyl halides [80] (Scheme 58). 

I. B. Campbell, The Sonogashira Cu-Pd-Catalyzed Alkyne Coupling Reactions, in Organocopper Reagents A Practical Approach (R. J. K. Taylor, Ed.), 217, Oxford University Press, Oxford, U. K., 1994. 

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