Organozinc, cross-coupling with

The first examples of microwave-assisted cross-couplings with organozinc compounds were recently reported [47]. In addition, the first high-speed synthesis of aryl boronates (Suzuki coupling reactants) has been performed under the action of single-mode irradiation with an in-situ-generated palladium carbene catalyst [48],... 

In addition, the organozinc compound obtained from ethyl 4-bromobutanoate reacts under similar conditions to those described previously, with 4-bromoacetophenone, to give the corresponding product in good yield15. The preparation of organozinc compounds and their cross-coupling with aryl halides can be carried out in one step (equation 7). 

Aryl mesylates are used for the Ni-catalysed cross-coupling with Grignard, organozinc and organoboron reagents [100]. 

The cross-conpling of more hindered secondary and tertiary alkyl hahdes has also been studied. Thus, secondary alkyl halides can be cross-coupled with organozinc reagents in the presence of the so-called pybox hgands (eqnation 9). 

Imidazole zinc reagent 372 was made from 2-iodoimidazole 371 with activated zinc dust. The organozinc reagent was cross-coupled with aryl iodides and alkenyl iodides, in good yields (Scheme 88), <1997T7237>. 

Yus, M., Gomis, J. Negishi cross-coupling with functionalized organozinc compounds prepared by lithium-zinc transmetallation. 

Bipyridines are readily prepared by cross-coupling reactions and the Negishi reaction is no exception [35]. Organozinc 99, prepared in standard fashion from 19, could be cross-coupled with 102 to generate 100. Triflate 102 was prepared from aminopyridine 101 via diazotization followed by formation of the triflate. 

Researchers at Pfizer were interested in preparing 3-aryl azetidines in efforts to identify new drug candidates for the treatment of asthma. A general approach was developed in which the organozinc species of the azetidine 29 was prepared via Zn insertion into the C-I bond followed by Pd-catalyzed cross-coupling with aryl halides. Using this process, 5-bromopyridine was coupled to produce 31 in 46% yield [17]. 

Haloboranes add to terminal alkynes in a cis /in-Markovnikov manner however, the bromoboration of acetylene itself exceptionally provides a trans adduct [28] (eq (17)). A sequence of haloboration with boron tribromide and then cross-coupling with organozincs is useful for a formal carboboration of alkynes with various organic groups. Addition of boron triboromide to allene is convenient for the synthesis of (2-bromo-2-propeny])borate [29] (eq (18)). 

---