Aryl halides alkylborane coupling

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... 

In the absence of base-sensitive groups in both alkylboranes and organic halides, PdCljCdppf) and sodium hydroxide in THF-HjO works nicely (Table 31.3, procedure A). For functionalized alkylboranes and halides, powdered sodium methoxide suspended in THF (procedure B) accelerates the reaction. However procedure B is less effective for vinylic halides. A promising coupling is achieved employing either potassium carbonate (procedure C) or potassium phosphate (procedure D), both suspended in DMF at 50 °C. The results also reveal that coupling reaction is applicable to iodides and bromides of vinyl and aryl halides (Chart 31.1) [2]. 

SCHEME 28.38 Coupling of aryl halides with alkylboranes. 

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). ... 

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... 

Primary alkylboranes derived by hydroboration of terminal alkenes with 9-BBN-H are coupled with aryl and alkenyl triflates and halides under properly selected conditions. The reaction proceeds smoothly without elimination of /1-hydrogen using PdCTklppf) or Pd(Ph3P)4 and K3PO4 in dioxane or DMF [132]. The intramolecular cross-coupling of the alkenyl triflate with the alkylborane in 292, prepared by in situ hydroboration of the double bond in 291 with 9-BBN-H, is applied to the annulation to... 

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]. 

In spite of these challenges, Suzuki and Miyaura [98] reported the first catalytic system in 1986 to cross-couple an alkylborane with aryl and alkenyl halides. Since... 

This section deals with the cross-coupling of vinyl halides with various types of organoboranes such as vinyl/aryl/alkylboranes. 

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