Cyanocuprates

Indol-2-ylcopper reagents can also be prepared from 2-lithioindoles and they have some potential for the preparation of 2-substituted indoles. 1-Methyl-indol-2-ylcopper can be prepared by reaction of 2-lithio-l-methylindole with CuBr[10]. It reacts with aryl iodides to give 2-aryl-1-methylindoles. Mixed cyanocuprate reagents can be prepared using CuCN[ll], The cyan-ocuprate from 1-methylindole reacts with allyl bromide to give 2-allyl-l-methylindole. 

A further improvement in the cuprate-based methodology for producing PGs utilizes a one-pot procedure (203). The CO-chain precursor (67) was first functionalized with zirconocene chloride hydride ia THF. The vinyl zirconium iatermediate was transmetalated direcdy by treatment with two equivalents of / -butyUithium or methyUithium at —30 to —70° C. Sequential addition of copper cyanide and methyUithium eUcited the /V situ generation of the higher order cyanocuprate which was then reacted with the protected enone to give the PG. 

As already noled, lower order cyanocuprates are more Su2 -selective reagents. On irealmenl widi acetale 163, however, a mixture of tlie iwo regioisomets was oblained fetilry 2) [81]. In addih on, y-alkylalion bad taken place witli ca. 2 596 loss ... 

Cupro-. cuprous, copper(I), cupro-. -chlorid, n. cuprous chloride, copper(I) chloride, -cy-aniir, n. cuprous cyanide, copper(I) cyanide cuprocyanide, cyanocuprate(I). -jodid, n. cuprous iodide, copper(I) iodide, -mangan, n. cupromanganese. -oxyd, n. cuprous oxide, copper(I) oxide, -salz, n. cuprous salt, cop-per(I) salt, -suifocyantir, n. cuprous thiocyanate, copper (I) thiocyanate, -verbin-dUDg, /. cuprous compound, copper(I) compound. 

The shift of the half-wave potentials of metal ions by complexation is of value in polarographic analysis to eliminate the interfering effect of one metal upon another, and to promote sufficient separation of the waves of metals in mixtures to make possible their simultaneous determination. Thus, in the analysis of copper-base alloys for nickel, lead, etc., the reduction wave of copper(II) ions in most supporting electrolytes precedes that of the other metals and swamps those of the other metals present by using a cyanide supporting electrolyte, the copper is converted into the difficultly reducible cyanocuprate(I) ion and, in such a medium, nickel, lead, etc., can be determined. 

Unsymmetrical coupling of vinylic, alkynyl, and arylmercury compounds was achieved in moderate-to-good yields by treatment with alkyl and vinylic dialkylcopper reagents (e.g., PhCH=CHHgCl -t- Mc2CuLi PhCH=CHMe). Unsymmetrical biaryls were prepared by treating a cyanocuprate ArCu(CN)Li (prepared from ArLi and CuCN) with an aryllithium Ar Li. ... 

An important type of mixed cuprate is prepared from a 2 1 ratio of an alkyllithium and CuCN.11 Called higher-order cyanocuprates, their composition is R2CuCNLi2 in THF solution, but it is thought that most of the molecules are probably present as dimers. The cyanide does not seem to be bound directly to the copper, but rather to the lithium cations.12 The dimers most likely adopt an eight-membered ring motif.13... 

In a mixed alkyl-thienyl cyanocuprate, only the alkyl substituent is normally transferred as a nucleophile. 

Another type of mixed cyanocuprate has both methyl and alkenyl groups attached to copper. Interestingly, these reagents selectively transfer the alkenyl group in conjugate addition reactions.16 These reagents can be prepared from alkynes via hydrozirconation, followed by metal-metal exchange.17... 

Entries 5 to 9 illustrate some of the modified reagents and catalytic procedures. Entry 5 uses a phosphine-stabilized reagent, whereas Entry 6 includes BF3. Entry 7 involves use of TMS-C1. Entries 8 and 9 involve cyanocuprates. In Entry 9, the furan ring is closed by a Mukaiyama-aldol reaction subsequent to the conjugate addition (Section 2.1.4). 

Hydrostannylation of terminal alkynes can also be achieved by reaction with stannyl-cyanocuprates. 

Cyanocuprates constitute a class of organocopper compounds that finds applications in organic synthesis.234 They are prepared by the direct reaction of an organolithium reagent and CuCN, with two different types of compounds being prepared depending on the stoichiometry employed the 1 1 ratio leads to RCu(CN)Li compounds whereas the 2 1 mixture affords R2Gu(GN)Li2. The lower- order or 1 1 cyanocuprates usually display the Cu-C-N-Li... 

Hydroxy stannanes can be prepared by cleavage of epoxides with BusSnLi or cleavage of epoxy stannanes with organocuprates (equation 33)72. The two methods are stere-ochemically complementary. The higher order cyanocuprate, Bu3Sn(Bu)Cu(CN)Li2, also affords /1-hydroxy stannanes by reaction with epoxides54. 

Lipshuz et al.42 have developed a new approach to the chiral biaryls mediated by cyanocuprate. The diastereoselective coupling depends on the proper choice of the tether (Scheme 8-13). 

A higher-order cyanocuprate, R2Cu(CN)Li2, reacts with a,P-unsaturated acylzirconocene chlorides at — 78 °C in THF to afford saturated ketones without giving a Michael-type product (Scheme 5.39). Treatment of the reaction mixture with D20 gives the [Pg.174]

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