Alkyl halides alkylborane coupling

Various aryl, alkenyl and even alkylborane reagents of different reactivity can be used for coupling with aryl, alkenyl, alkynyl and some alkyl halides, offering very useful synthetic methods. The cross-coupling of aryl and heteroarylboronic acids with aryl and heterocyclic halides and triflates provide useful synthetic routes to various aromatic and heteroaromatic derivatives. Sometimes, the reaction proceeds in the... 

Photocatalytic carbonylative coupling with 9-alkyl-9-borabicyclo[3.3.1]-nonanes (9-R-9-BBN), however, made it possible to transform alkyl halides to ketones [72]. lodoalkenes or iodoalkynes are thus cyclized to five-membered rings [73]. The oxidative addition of iodoalkyl to palladium(O) proceeds via radicals allowing the ring closure to take place prior to the dual coupling with CO and the alkylboranes. 

Alkylboranes 103 are easily prepared by hydroboration of 1-alkenes with 9-BBN, and subsequent reactions with aryl, alkenyl, and alkyl halides offer versatile methods of dkylation to afford alkylated products 104, 105, and 106. The hydroboration-coupling protocol has been utilized extensively in natural product syntheses [87]. 

Trialkylboranes, including 9-alkyl-9-BBN, underwent cross-coupling with 1-alkenyl or aryl halides or triflates.750,751 The reaction was limitedly used for primary alkylboranes thus, hydroboration of terminal alkenes with 9-BBN was the most convenient to furnish the desired boron reagents in the presence of a base and PdCl2(dppf)750,751 or PdCl2(dppf)/2Ph3As (Equation (200)).752... 

Vinyl halides 116 also undergo facile 5-Alkyl Suzuki (sp -sp ) coupling with B-alkylboranes (Scheme 28.31). Although several palladium catalysts can be utilized for this coupling, the preferred catalyst for 5-Alkyl Suzuki reaction is diphenylphosphinoferrocenyl palladium dichloride (PdCl2(dppf)) 118 (Figure 28.4) due to its favorable bite angle and reduced possibility of... 

B-Alkyl Suzuki coupling offers tremendous opportunities for one pot CTOSS-coupling between any alkene and aryl halides, as the intermediate alkylboranes are typically not isolated and can be used in situ for further cross-coupling. Some of the representative examples of this coupling include the synthesis of pyridyl alcohols 148 (Scheme 28.41), synthesis of alkyl arenes 149 (Scheme 28.42), and coupling of cyclopropyl boronic acid with aryl halides to obtain cyclopropyl arenes 153 (Scheme 28.43). ... 

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