Alkynes Negishi cross-coupling reaction

Cross-coupling reactions 5-alkenylboron boron compounds, 9, 208 with alkenylpalladium(II) complexes, 8, 280 5-alkylboron boron, 9, 206 in alkyne C-H activations, 10, 157 5-alkynylboron compounds, 9, 212 5-allylboron compounds, 9, 212 allystannanes, 3, 840 for aryl and alkenyl ethers via copper catalysts, 10, 650 via palladium catalysts, 10, 654 5-arylboron boron compounds, 9, 208 with bis(alkoxide)titanium alkyne complexes, 4, 276 carbonyls and imines, 11, 66 in catalytic C-F activation, 1, 737, 1, 748 for C-C bond formation Cadiot-Chodkiewicz reaction, 11, 19 Hiyama reaction, 11, 23 Kumada-Tamao-Corriu reaction, 11, 20 via Migita-Kosugi-Stille reaction, 11, 12 Negishi coupling, 11, 27 overview, 11, 1-37 via Suzuki-Miyaura reaction, 11, 2 terminal alkyne reactions, 11, 15 for C-H activation, 10, 116-117 for C-N bonds via amination, 10, 706 diborons, 9, 167... 

Replacing the terminal alkyne by an arylzinc, an aryltin, or an arylboron compound leads respectively to the Negishi, Stille, or Suzuki aromatic cross-coupling reactions. There is no need for a cocatalyst, but the Suzuki reaction requires a nucleophilic base such as aqueous carbonate (Figure lie) (or fluoride) [17b, 22]. 

Utilization of stereodefined alkenylalanes or alkenylzirconium reagents in palladium-catalyzed cross-coupling reactions greatly enhances the versatility of Negishi-type coupling reactions. These organometallics are readily available by hydroalumi-nation, carboalumination, and hydrozirconation of alkynes, respectively. 

As with the Negishi and Suzuki reactions, the same solid-support (vide supra) could be adapted to the Sonogashira reaction [62]. The solid-supported bromopyridine 178 could undergo cross-coupling reactions with a variety of alkynes and be released from the solid-support to allow isolation of 331. 

For the copper-free Sonogashira reaction, the mechanistic study reported in this thesis revealed that, just like in other cross-coupling reactions (i.e. Stille, Negishi), there are several competing reaction pathways and a change on the reaction conditions (e.g. solvent, ligands, substrates, base) might favor one over the other ones. Moreover, a new mechanism in which the acetylide (formed by deprotonation of the alkyne) directly reacts with the catalyst was also proposed. 

There is no doubt that one of the most useful functionalizations of alkynes is Negishi methylalumination of terminal alkynes [21]. This reaction is catalyzed by the zirconocene 1 and the addition of trimethylaluminium proceeds regioselectively through a stereoselective s/n-addition to give the cis-methylalkenylalanes 33, which can be used in further reactions with electrophiles or cross-coupling reactions (Scheme 13). This method will not be... 

The hydrozirconation of alkynes with Cp2ZrHCl (Schwartz s reagent) provides ready access to vinylzirconium reagents, which have been shown to be suitable partners in palladium-catalyzed cross-couplings ( zirconium-Negishi reaction ) with aryl and vinyl electrophiles [1]. Recently, Fu disclosed the first... 

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