Suzuki-Miyaura reactions, with

The pincer-type palladacycle (120) (R = 1Pr), which is actually a derivative of a dialkylphos-phinous acid (themselves excellent ligands see Section 9.6.3.4.6) was shown to allow the crosscoupling of aryl chlorides with terminal acetylenes ((120), ZnCl2, Cs2C03, dioxane, 160 °C). However the high reaction temperature may be prohibitive for the actual application of this catalytic system, as acetylenes are known to be thermally sensitive.433 The same palladacycle (R = Ph) is effective in the Suzuki-Miyaura reaction with aryl bromides and activated aryl chlorides (K2C03, toluene, 130 °C). 

The Suzuki-Miyaura reactions with relatively inert arylchloride are known to require palladium complexes possessing highly electron-rich ligands which favor the oxidative addition of the arylchloride into Pd(0)-complex (Scheme 11) [67-69]. Herrmann et al. showed that the utilization of NHC ligands with bulky substituents... 

Scheme 48 Suzuki-Miyaura reaction with an aryl chloride...

For the synthesis of a cavitand functionalized with terpyridyl groups via rigid linkages, transition metal catalyzed cross-coupling reactions are especially well suited. Starting with the boronic acid ester 48 [65], attachment of the terpyridyl groups to the cavitand was realized by Suzuki-Miyaura reaction with the tetraiodo-cavitand 47 (Fig. 15). 

Table6.6 Results obtained forthe continuous flow Suzuki-Miyaura reaction with Pd(ll) catalyst 69.

Scheme 15.22. Suzuki-Miyaura reaction with 4,5-dichloropyridazinones.

A microwave mediated Suzuki-Miyaura reaction with an unprotected tetrazole moiety has also been evaluated. This was reported as the first Suzuki-Miyaura coupling known to proceed without protection of the N-2 position of the tetrazole (Scheme 15.24) [61]. 

Suzuki-Miyaura reactions with aryl bromides and triflates have been reported in the synthesis of plasmepsin I and II inhibitors using a hydroxyethylamine transition-state-mimicking scaffold [73], Four libraries of similar compounds were prepared where the Suzuki-Miyaura reaction was used for direct derivatization of the PI -position without protection of the hydroxyethylamine center. It was noted in this context that no epimerization occurred during the reaction and that exchange of cesium carbonate for sodium carbonate resulted in better yields (Scheme 15.33) [74]. 

Diastereoselective version of the Suzuki-Miyaura reaction was accomplished using planar chiral tricarbonylchromium-complexed aryl bromide with arylboronic acids to form the respective biaryls with very high diastereomeric excess (d.e.) For example, compound 582 underwent the Suzuki-Miyaura reaction with boronic acid 583 to give the biaryl 584 in 88% yield [20], Scheme 7. 

Hydroboration of exocyclic enol ether 111 with 9-BBN and following Suzuki-Miyaura reaction with enol triflate 128 proceeded smoothly to generate the cross-coupled product 129 in 81% yield (Scheme 17). Not unexpectedly, the corresponding enol phosphate of 128 proved to be a poor substrate for this complex fragment coupling. Given the structural complexity and sheer size of the respective fragments, this remarkable yield (81%) represents... 

Chatani et al. [137] have reported on nickel-catalyzed Suzuki-Miyaura reactions with aryl fluorides as the cyclometalation substrates, as shown in Eqs. (8.27) and (8.28). 

Palladium nanoparticles and other heterogeneous catalysts are often invoked as catalysts in cross-coupling processes [194, 195). Direct evidence in support of an oxidative-addition-promoted leaching mechanism has been recently obtained in the Suzuki-Miyaura reactions with nanoparticle catalysts, suggesting that true surface catalysis remains largely unknown with these heterogeneous catalysts [196]. 

An ESI-MS/MS study by CID (collision-induced dissociation) of the Suzuki-Miyaura reaction with palladium-diene catalysts showed that in this system, the reductive elimination step determines the rate of the whole process [361],... 

A ramification of the DreM strategy in an unusual heteroaromatic framework is illustrated in the synthesis of the previously unknown triazadibenzo[cd,/]azulen-7(6H)-one 75 in which the imidazopyridines 70 and 71 are coupled by a Suzuki-Miyaura reaction with the DoM-derived boronic add 72 to give 73 and 74, respectively (Scheme 14.18). Compound 74 undergoes DreM cyclization on treatment with LiTMP to give the potentially bioactive 75 in modest yields [126]. 

SCHEME 19.43 Mechanism of the Suzuki-Miyaura reaction with wBu NOH as the base and the inhihiting role of countercations m. ... 

On the other hand, vinylBhg was disearded for the 100 g seale synthesis of the latex monomer HESS (4-hydroxyethylsulfonylstyrene, Seheme 3.22), because the Suzuki-Miyaura reaction with the aryl bromide was found to be capricious. Commercial potassium vinyltrifluoroborate was ultimately chosen despite the added cost. 

Table 3.2 Examples of products obtained from a Suzuki-Miyaura reaction with vinylBhg. 

Scheme 3.23 Suzuki-Miyaura reaction with a styryl boronic ester. (Adapted with permission from ref. 90 2013 American Chemical Society.)...

Suzuki-Miyaura reaction with Boc-protected aminomethyltrifluoroborate reported by Molander and Shin [139b]. 

Synthesis p-Phenylanisole via the Suzuki-Miyaura Reaction with a FibreCat-1034 Catalyst... 

Scheme 49 Palladium-catalyzed Suzuki-Miyaura reactions with bromothiophenes [342]... 

Negishi cross-coupUng of 170 to 171 were catalyzed by acenaphthoimi-dazolylidene palladium complexes (2013JOC7436), and a similar catalyst was able to induce a Suzuki—Miyaura reaction with the stericaUy hindered boronic acid, Scheme 68 (20120L4250). 

Other Suzuki—Miyaura reactions with 9-chloroacridine employed pal-ladium(II)acetate in the presence of a carbazolyl-derived phosphine hgand... 

Firooznia has reported the synthesis of 4-substituted phenylalanine derivatives via cross-coupling of protected (4-pinacolylboron)phenylalanine derivatives such as 61 with aryl and alkenyl iodides, bromides and triflates [44]. They have further shown that BOC derivatives of (4-pinacolylboron)phenylalanine ethyl ester 61 or the corresponding boronic acids undergo Suzuki-Miyaura reactions with a number of aryl chlorides in the presence of PdCl2(PCy)3 or NiCl2(dppf), respectively providing diverse sets of 4-substituted phenylalanine derivatives of type 62 [45]. This strategy has also been used for the synthesis of enantiomerically enriched 4-substituted phenylalanine derivatives (Scheme 3.28) [46]. 

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