Organo-copper reagents, coupling

Alkynyl(phenyl)iodonium salts can be efficiently coupled with various organo-copper reagents. Direct coupling of alkynyliodonium tosylates 132 with vinyl-... 

Propanedithiol, 50,72 Propargyl bromide, coupling with an organo-copper reagent, 50, 98 a-Pyrone, irradiation of, 50, 23... 

R -R, is formed (Sheppard, 1970). Therefore, reaction of certain organo-coppers with excess cuprates, followed by oxidation, can lead to selective cross-coupling (Corey and Katzenellenbogen, 1969 Whitesides et al., 1969b). Reverse addition of organolithium compounds or Grignard reagents... 

Allylic acetates or related compounds can also be displaced by organo-cuprates. A synthetic approach to prostaglandins (PC s) via cross-coupling of a vinylic copper reagent with an allylic electrophile has been elaborated (Corey and Mann, 1973). Notably the reaction of LXI and LXII proceeds exclusively by an Sn2 pathway. 

Two useful syntheses of fatty acids have appeared. Coupling of the chloro-magnesium salts of w-bromoacids with alkyl Grignard reagents via an organo-copper(i) ate complex is shownto be most effective for longer chain acids (e.g. palmitic acid in 94% yield), whereas an efficient route to o -methyl labelled fatty acids proceeds via methyl cadmium chloride (Scheme 5). 

The zinc organo-lialide is prepared for use by heating together the zinc-copper couple, the alkyl or aiyl halide, ethyl acetate, and toluene for about an hour, the reaction being started if necessary with a ciystal of iodine. All the reagents must be well dried, and the colomdess viscous liquid which results is ntilised by adding to it the acid chloride dissolved in toluene, and when the required amount has been added the intermediate zinc complex is decomposed by the addition of dilute sulphuric acid.1... 

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