Borylation with diboron reagents

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

Most metal-boryl complexes have been synthesized by salt elimination or oxidative addition. Examples of these reactions are shown below. Ottier less common routes to metal-boryl complexes include transmetaUation of a boryl group from one transition metal to another and reactions of boranes with metal-olefin complexes. Boryl complexes have also been generated as intermediates in catalytic processes by "transmetaUation" of a metal halide with a diboron reagent. ... 

Within the last decade, another source of diboron activation has been promoted in basis to the efEcient application to catalysis. This is the use of nanoparticles which can interact with the diboron reagent and develop an enhanced performance toward diboration reaction. Fernandez observed in 2008 that the in situ formation of Au nanoparticles, from Au(I) complexes, could not only activate the B2cat2 but also deliver the boryl units on alkenes with total chemoselectivity. " The gold nanoparticles were estimated to have a mean crystaUite size of 10.5 0.3 nm. The gold nanoparticles were stabilized by 2,2 -bis-(diphenylphosphino)-l-l -binaphthyl (BINAP), diphenylphosphinoethane (DPPE), and L-glutathione. The core size and size distribution ofBINAP-Au nanoparticles were examined by transition electron microscopy (TEM), and the image shows disperse nanopartides 6.9 3.0 nm in diameter (Fig. 6). 

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. 

Borylation at the terminal -carbon atom of allylsilanes with bis(pinacolato)diboron furnishes a valuable reagent for homologation and/or functionalization by two different reactions. ... 

It seems that all the efforts to activate tetra(alkoxy)diboron compounds are justified since the model CI2B—BCI2 reagent, which develops borylation without metal activation, is too difficult to handle. However, the progress in this field has opened a new window toward the activation of tetra(alkoxy) diboron compounds in a metal-free context by the formation of Lewis add—base adducts and their addition to unsaturated substrates can be performed with total chemo-, regjo-, and stereoselectivity. 

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