Alkylboronates, cross-coupling

Through the use of arenediazonium salts, the straightforward transformation of amines into cross-coupling products can be realized. Whenever the diazonium salts do not tolerate bases and strong nucleophiles (e.g., phosphines), base- and phosphine-free protocols have to be used. Heterocyclic carbene ligands serve well in cross-coupling of Aryl- and vinylboronic acids, or alkylboronates with arenediazonium salts.369,370 Several convenient phosphine-free protocols have been developed for the same purpose.371-373... 

Alkylboron boron compounds, cross-coupling reactions,... 

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... 

The hydroboration-coupling approach for the construction of carbon skeletons affords several advantages [139]. The high stereoselectivity of the hydroboration reaction provides a stereodefined alkyl center on boron. For instance, in the reaction shown in Scheme 2-49, the hydroboration occurs chemoselectively at the less hindered C(19)-C(20) double bond. In addition, the alkylboron group thus constructed can be readily cross-coupled with alkenyl or aryl halides under mild conditions. 

Molander, G. A., Yun, C.-S. Cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides. Tetrahedron 2002, 58, 1465-1470. 

Suzuki-Miyaura cross-coupling reactions of alkylboronic acid derivatives or alkyltrifluoroborates widi aryl, alkenyl or alkyl halides and triflates ,... 

In 2002, Fu described a Pd/P(t-Bu)2Me-based catalyst that can achieve room-temperature cross-couplings of primary alkyl bromides with aryl-, vinyl-, and alkylboronic acids (Eq. 5) [ 17]. KOf-Bu was the best activator among those that were examined, and a protic solvent (t-amyl alcohol) was found to be optimal. 

An electronically and sterically diverse array of arylboronic acids serve as useful reaction partners (Table 2, entries 1-4). In addition, vinylboronic acids can be cross-coupled in good yield (entry 5), although reactions of alkylboronic acids proceed with somewhat lower efficiency (entry 6). The catalyst tolerates a range of functional groups, including esters, thioethers, and cyanides. 

Suzuki-Miyaura Cross-Coupling Reactions of Alkylboronic Acid Derivatives or Alkyltrifluoroborates with Aryl, Alkenyl or Alkyl Halides and Triflates Doucet, H. Eur. J. Org. Chem. 2008, 2013. 

Keywords Allyl bromides, benzyl bromides, diborylmethane derivative, Pd-catalysts such as [Pd-PEPPSI-IPr] (l)/Pd[P(f-Bu)3l2 (2), aq. KOH, dioxane, room temperature, Suzuki-Miyaura cross-coupling (SMC) reaction, C-C bond formation, regio- and chemoseletivity, homoallylboronates, alkylboronates... 

Abe, S. Miyaura, N. Suzuki, A. 1992. The palladium-catalyzed cross-coupling reaction of enol acetates of a-bromo ketones with 1-alkenyl-, aryl-, or alkylboron compounds A facile synthesis of ketones and their enol acetates. J. Am. Chem. Soc. 65 2863-2865. 

Cross-coupling of Boronic Acids. Ag20 can significantly enhance the reactivity of various boronic acids in Suzuki-Miyaura cross-coupling reactions. Alkylboronic acids, which, oftentimes, lead to poor conversions of the desired coupled product, are rendered more reactive by the addition of Ag20 (eq 24). Use of excess Ag20 facilitates the cross-coupling of various unactivated w-alkylboronic acids to either aryl or alkenyl halides/trifiates. The reaction conditions are very mild and furnish excellent yields of the desired coupled product. 

Ag20 was also found to promote cross-coupling between aryl-boronic acids and terminal alkynes (eq 27). Reactions worked well with both electron-donating and electron-withdrawing groups present on the boronic acid. Alkylboronic acids, on the other hand, were inert under these conditions and furnished only the homocoupled product. Electron-deficient alkynes, which under standard conditions fail to react, produced the desired coupled products in good yields. 

Alkylboronates and aryl halides have been cross-coupled in the polymerization reactions shown in equations 97-99 241). 

Scheme 3.84 Ag(l)-promoted Suzuki-Miyaura cross-coupling of functionalized n-alkylboronic acids.

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