SYNTHESIS aryltrifluoroborates

Table 13. Synthesis of biatyls from diaryliodonium salts and potassium aryltrifluoroborates [52]...

The synthesis of relevant biaryls has also been reported with aryltrifluoroborates directed by the carboxylic acid functional group in addition to oxidative dimerization. Sanford has described the preparation of biaryls via two discrete C—H functionalizations through the intermediacy of a Pd(IV) fcis-cyclopalladated moiety which reductively eliminates to afford the new C—C bond (Scheme 3.3). An analogous procedure affording the homo-coupled arene from the unactivated starting material has also been reported. ... 

One-pot Synthesis of Arylboronic Acids and Aryltrifluorobo-rates. Hartwig also reported the synthesis of arylboronic acids and aryltrifluoroborates in a one-pot sequence by Ir-catalyzed borylation of arenes followed by the oxidative cleavage of the boronate ester with NaI04 and the displacement of pinacol by KHF2, respectively (eq 4). These two-step sequences give products that are more reactive and selective in the subsequent chemistry, such as Suzuki coupling, than the initially formed pinacol-boronates. 

SCHEME 1.3 Synthesis of alkyl aryl ethers using aryltrifluoroborate salts [7],... 

Can the iridium chemistry tolerate substrates with primary alcohols Need to generate an aryltrifluoroborate salt Yes, a version of the iridium-catalyzed C—H borylation is tolerant to the presence of primary alcohols [75] A convenient precursor for the direct synthesis is not readily available. Try generating an arylboronic acid or arylboronate, and treat it with a solution of KHP [37, 38]. For arylboronates, a 4 1 THF/water mixture was successful [38]... 

Another approach to the conversion of aryltrifluoroborate salts into aryl fluorides also used a common copper salt to promote the reactions however, this chemistry used an electrophilic source of fluorine (Scheme 7.58) [84]. The most effective source of F was found to be A-fluoro-2,4,6-trimethylpyridinium ttiflate. Similar to the authors previous work with arylstannanes, the key to the synthesis was prestirring the F source and the copper complex prior to the introduction of the aryltrifluoroborate salts. Using this system, a wide range of aryltrifluoroborate salts bearing ethers, halogens, aldehydes, ketones, amides, and esters were converted into aryl fluorides. 

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