Reagents copper iodide

This complex should be used when the organolithium is in solution in a hydrocarbon solvent. For organolithium reagents prepared in ether (see Note 4), the same complex may be used or, more conveniently, copper iodide (Cull can be used. The Cul purchased from Prolabo or Merck 4 Company, Inc. may be used directly. Other commercial sources of Cul (Fluka, Aldrich Chemical Company, Inc., Alfa Products, Morton/Thiokol, Inc.) furnish a salt which affords better results when purified. 1 mol of Cul is stirred for 12 hr with 500 ml of anhydrous tetrahydrofuran, then filtered on a sintered glass funnel ( 3), washed twice with 50 ml of anhydrous tetrahydrofuran, once with 50 ml of anhydrous ether and finally dried under reduced pressure (0.1 imO for 4 hr. 

Copper iodide acts as an efficient reagent for the nucleophilic displacement of 1-haloalkynes. It transforms 1-bromoalkynes (72) into 1-iodoalkynes (73) which, on further treatment with copper(II) bis(arenesulfinate), are converted into the corresponding alkynyl aryl sulfones (74). An electron transfer between 1-haloalkynes and copper(I) salts is believed to take place for the copper-assisted halogen-exchange reaction at the acetylenic carbon atom. 

Formation of 772-complexes is known for both mono- and bis-phospho-nio-benzophospholides and has been observed (Scheme 18) in the reactions of the cation 23 with Jonas reagent to give the cobalt complex 49 [49], addition of the zwitterion 25 to a Mo-Mo triple bond to afford the dinuclear complex 50 [47], and finally, upon treatment of 26 with copper iodide to yield the complex 51 [46] which is peculiar because of the presence of the same ligand in two different coordination modes. Whereas it is clear that the metal atoms in all complexes supply inappropriate templates for the formation of 77 -complexes, the preference of rf-(,n)- over a possible a-coordina-tion is less well understood [49]. 

The nucleophilic nature of this reagent is confirmed by the p-value + 0.46 obtained from the crude Hammett plot of the reaction of p-substituted iodoaromatics with the trifluoromethylating system sodium trifluoroacet-ate / copper iodide [88JCS(P1)921]. Consequently, electron-withdrawing substituents enhance reactivity, whereas electron-donating substituents (—OH, —NH2) inhibit the reaction. 

The nature of organocopper reagents appears to be dependent on the method of preparation and the stoichiometry. Specific examples are methylcopper (76, 310), phenylcopper 73), and pentafluorophenyl-copper 34, 37, 147). The best method of preparing pentafluorophenyl-copper of composition CeFsCu appears to be via the addition of copper(I) bromide to pentafluorophenylmagnesium bromide 34, 37), since the lithium reagent and copper iodide gives an ate complex 147). An ate complex was also obtained from pentafluorophenyllithium and silver chloride in equimolar proportions 265). As shown in Table III, many of the isolated copper compounds gave somewhat incorrect or irreproducible analyses, and others contain metal halide and solvent molecules. 

Interestingly, Marshall [50-52] found that on addition of a Grignard reagent to the tetrasubstituted allylic phosphate 111, in the presence of 1 Eq of copper iodide in dimethoxyethane and dimethylsulfide, the sole product formed was the SN2-coupled compound 112 in good yield (82%) [Eq. (35)]. 

More recently, Hudlicky [69] reported the regio- and chemoselectivity of the reaction between homochiral vinyloxiranes and Grignard reagents in the presence of a catalytic amount of copper iodide [Eq. (57)]. 

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