Borylation of aryl halide

Pinacolborane is extensively used in the borylation of aryl halides 114 in the presence of a base (typically pyridine or Et3N or KOAc) and catalytic amount of PdCl2(DPPF) to furnish aryl boronates 115 (DPPF = l,l -bis(diphenyl-phosphino)ferrocene Equation 7) <1997JOC6458, 2000JOC164>. Pinacolborane is compatible with esters, ketones,... 

Murata, M., Oyama, T., Watanabe, S., Masuda, Y. Palladium-Catalyzed Borylation of Aryl Halides or Trifiates with Dialkoxyborane A Novel and Facile Synthetic Route to Arylboronates. J. Org. Chem. 2000, 65,164-168. 

Marshall, J. A. Pd-catalyzed borylation of aryl halides. Chemtracts 2000, 13, 219-222. 

No report was found on a good yielding distillation of HBnpg. Solutions of HBnpg have been prepared and used in situ although the reagent exhibits poor purity ( H NMR), it can be used in an efficient Ni-catalyzed borylation of aryl halides. i" " ... 

The PdCl2(CH3CN)2-catalyzed phosphination and borylation of aryl halides have also emerged as powerful methods for carbon-phosphorus and carbon-boron bond formation, respectively. 

If the substrate does not c ntam electrophiles, try a one-pot magnesiation/borylation of aryl halides using pinacolborane [2]... 

Ito designed a metal-free approach to the borylation of aryl halides using a silylborane as the borylating agent (Scheme 6.33) [3]. The reaction conditions were quite mild, and a host of functionalized aryl halides were converted into arylboronates. Substrates bearing esters, halogens, amides, and unprotected amines were well tolerated. The chanistry also converted bulky aryl halides into arylboronates. For example, bromo-2,4,6-triisopropylbenzene... 

Kleeberg C, Dang L, Lin Z, Marder TB. A facile route to aryl boronates room-temperature, copper-catalyzed borylation of aryl halides with alkoxy diboron reagents. Angew Chem Int Ed Engl. 2009 48 5350-5354. 

In contrast to the borylation of alkane C-H bonds, the coupling of aryl halides with amines was based on a literature precedent from another group published about a decade before our initial studies. Kosugi, Kameyama and Migita published the coupling of aryl halides with tin amides." Mechanistic studies we conducted on this process led us to the perhaps obvious realization that the reaction" could be conducted with amines and a silylamide base instead of tin amides (equation 4)." Surveys of bases with similar p a values led Janis Louie to conduct reactions with alkoxide bases. Similar studies were conducted at nearly the same time by Steve Buchwald and coworkers."... 

Palladium-catalyzed reaction of aryl halides with diboron reagent to produce aryl-boronates. Also known as Hosomi-Miyaura borylation. 

Another resin-capture approach has been pubhshed in relation to the synthesis of tetrasubstituted ethylenes via Suzuki coupling reactions (Scheme 20) [42, 53]. A 25-member hbrary was synthesized using five alkynes, five aryl halides, and a polymer-bound aryl iodide. The alkynes 55 were converted into bis(boryl)alkenes 56 in solution, and the crude intermediates were used in Suzuki reactions with an excess of aryl halide. When all of the bis(boryl)alkene 56 had been consumed, the aryl iodide resin 59 was added to the reaction mixture and the reaction continued on the solid support. Side products such as 58, arising from a double Suzuki reaction, remained in solution and could be washed away. Compounds 60 were cleaved from the polymer using trifluoroacetic acid and products 61 were obtained in > 90% purity. 

Aryl chlorides typically do not react under these conditions. However, Miyaura has been able to extend the scope of this reaction to include aryl chlorides by changing the catalyst system to Pd(dba)2 and PCys and replacing pinacolborane with bis(pinacolato)diboron. Vinyl iodides and trifiates undergo borylation with pinacolborane under similar conditions in the presence of triphenylarsine (AsPEb) (eq 17). Benzylic halides react with pinacolborane in the presence of PdCl2, PPhs, and N,N-diisopropylethyl amine (eq 18). Borylation of allylic halides in the presence of Pt(dba)2, AsPhs, and EtsN leads to highly regio-and stereoselective allylboronates (eq 19). 

In contrast to the rare occurrence of the oxidative addition of C-C bonds, the oxidative addition of the nonpolar bonds between two main group atoms, such as boron and silicon, can be facile. The oxidative addition of Si-Si bonds in disilanes and the B-B bond in diborane(4) reagents is likely to be a step in a variety of catalytic reactions, including the additions of disilanes, - diborane(4) reagents, and silaboranes - across olefins and alkynes, the silylation and borylation of arene C-H bonds, - - the borylation of alkane C-H bonds, and the conversion of aryl halides to arylsilanes and arylbo-ronate esters. " ... 

Thus the catalyzed borylation of aryl iodides, bromides, chlorides or sulfonates with HBhg proceeds readily, in excellent yields and chemoselectivi-ties. The products are perfectly stable to air, water and chromatography. It can thus be considered as a good, inexpensive alternative to the analogous Pd-catalyzed borylation with HBpin, particularly when the substrates are sulfonates or electron-rich halides. 

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