Boronic compatibility with oxidative methods

Besides the one-pot process described above, the White Reagent catalyzes a chelate-controlled oxidative Heck arylation between a wide range of a-olefins and organoborane compounds in good yields and with excellent regio-and stereoselectivities (Figure 6). Unlike other Heck arylation methods, no Pd-H isomerization is observed under the mild reaction conditions. Aryl boronic acids, styrenylpinacol boronic esters, and aryl potassium trifluoroborates (activated with boric acid) are all compatible with the general reaction conditions. 

In this section, we refer to some Stille reactions that serve as representative examples. As noted before, the Stille reaction is compatible with boronic esters. " Therefore, the Stille cross-coupling provides a simple method for homologation of aryl-and 1-alkenylboronic esters (Scheme 5-60). Since the carbon-boron bond is inert to transmetalation in the absence of a base and oxidative addition of the carbon iodide bond is faster than that of the carbon bromine bond, the arylation of iodoboranes with arylstannanes selectively occurs at the carbon iodo bond without affecting the other onej l In addition. Scheme 5-60 also shows a Stille reaction having a multitude of functional groups such as being present in a modified nucleotide. ... 

In addition to the notable regio- and chemoseleetivity observed in boron haUde-mediated ether cleavage reactions, the compatibility of these reagents with a wide variety of functional gronps is quite remarkable. For example, boron trichloride effleiently eleaves benzyl ethers andketals without affecting the imine A-oxide functionality in nitrones (Seheme 23.5). The method was used in the efficient syntheses of polyhydroxylated A-hydroxypyrrolidines and A-hydroxyiminosngars. 

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