Cuprates as Selective Metalating Reagents for Aromatic Halides

Reductive coupling reaction of benzyl, allyl and alkyl halides in aqueous medium promoted by zinc

“…14, No. 3,2003 of basic solutions increased remarkably the yields from 13% in NH 4 Cl solution (Table 1, entry 16) to 23% in K 2 HPO 4 /Na 2 HPO 4 (pH 7) and finally to 69% in K 2 HPO 4 solution (pH 12) ( Table 2, entries 9 and 3). However, for pH higher than 12 a deleterious effect on the yield was observed (entries 10, 11 and 12).…”

“…14, No. 3,2003 In an attempt to take advantage of the great difference in reactivity of structurally different halides, cross coupling reactions were performed with benzyl bromide, allyl bromide and t-butyl iodide using methods A, B and C as well other conditions. The best results were obtained with a aqueous KOH solution and CuCl 2 as catalyst; however, the cross coupling products were observed only in moderate yields along with the homocoupling products ( Table 6).…”

“…The synthesis of biaryls is usually accomplished by dimerization of aryl halides catalyzed by nickel or palladium complexes in the presence of a reducing agent such as zinc powder 3 or upon electrochemical reduction. The homocoupling of several organic halides has been performed in good yields under anhydrous conditions, in some cases using activated metals, 4 and the interest for these reactions has increased.…”

Sterically Hindered Lithium Dialkylcuprates for the Generation of Highly Functionalized Mixed Cuprates through a Halogen���Copper Exchange

“…[1] Among several approaches, an organosulfone-mediated approach is very effective for allylation, [2] vinylation, [3] and azidation [4] [Eq. (1), AIBN ¼ 2,2'-azobisisobutyronitrile].…”

“…Kondo et al have shown that the use of lithium dimethylcuprate allows an iodine±copper exchange with a functionalized aryl iodide that bears an ester group. [4] In this case, an excess of Me 2 CuLi (2 equiv) has to be used to quench the methyl iodide formed in the I/Cu-exchange reaction. In contrast, the readily prepared lithium dineopentylcuprate (Neopent 2 CuLi, 1) and (PhMe 2 CCH 2 ) 2 CuLi, (Neophyl 2 CuLi, 2) [5] rapidly react with various functionalized iodides of type 3 to give mixed organocuprates of type 4, which selectively transfer the aryl group [6] to electrophiles (E þ ), thus leading to products of type 5 (Scheme 1).…”