Copper cross-coupling reactions with

As well as alkenylstannanes [106-108], other classes such as a-heteroatom-substituted alkyltributylstannanes [109] and, more importantly, allylic stannanes [110, 111] also undergo these Sn-Cu transmetalations. Otherwise difficult to prepare, allylic copper reagents may, however, be obtained by treatment of allylic stannanes (produced in turn from organolithium, magnesium, or zinc organometallics) with Me2CuLi LiCN. They enter into cross-coupling reactions with alkyl bromides [110] or vinyl triflates (Scheme 2.52) [111]. 

Chiral butenolides are valuable synthons towards y-butyrolactone natural products [37] and have also been successfully applied to the synthesis of paraconic acids. The lactone 91, readily available from the hydroxyamide (rac)-90 by enzymatic resolution [38] followed by iodolactonization, proved to be an especially versatile key intermediate. Copper(I)-catalyzed cross coupling reactions with Grignard reagents allowed the direct introduction of alkyl side chains, as depicted in 92a and 92b (Scheme 13) [39, 40]. Further... 

The cross-coupling reaction with non-activated iodoalkenes proceeds well only by using a polar solvent like NMP or DMPU [29] and elevated reaction temperatures (60 °C, 12 h). The compatibility of the zinc-copper reagents with these harsh reaction conditions shows the remarkable thermal stability of zinc-copper organometallics. The cross-coupling reaction occurs with complete retention of the configuration of the double bond and allows the stereospecific synthesis of highly functionalized alkenes like 29 (see Section 9.6.6 Scheme 9-27) [57],... 

Imidazoles and fused-derivatives have participated in a myriad of cross-coupling reactions. 2-Thiomethylrmidazolm-5-one 102 underwent efficient palladium-catalyzed cross-coupling reactions with boronic acids in the presence of copper(l)thiophene-2-carboxylate (CuTC) to give... 

A cross-coupling reaction with tin derivatives Ar SeSnBu3 was carried out for various Ar(Het)Br in good to high yields using Cu(I) complexes (Scheme 3.25) [56]. The copper catalyst has shown much better performance than Pd and Ni systems in... 

In addition to the above-mentioned allylic alkylation reactions, catalytic-in-copper C(sp )-C(sp ) cross-coupling reactions with alkylzincs can be achieved with some other specific electrophiles. For instance, the benzylzinc reagent 127, prepared in the presence of LiCl, undergoes coupling with the benzyl bromide 128 in the presence of only 0.4mol% CuCN-2 LiCl, with a yield of 89% (Scheme 4.29) [112, 113]. 

Table 5.11 Reaction of copper anion with organohalides and subsequent cross-coupling reactions with benzoyl chloride.

Recent Advances in Copper-promoted C-Heteroatom Bond Cross-coupling Reactions with Boronic Acids and Derivatives... 

The palladium catalyzed cross-coupling of 3a with phenylacelylene was found to lead to decomposition of the acetylene and recovery of 3a. In another model study we employed 3c in the Stille cross-coupling reaction with acid chlorides and found the reaction led to the formation of ketone, but also several additional by-products. With so many side-reactions we deemed the reaction unsuitable for polymerization studies. We did find that the iodo derivatives undergo facile palladium/copper catalyzed alkynylation and were successful in preparing copolymer 6 (Scheme 3). Copoljuner 6 was produced in high yield and purity [M = 67,000, polydispersity 3.8]. 

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