Arylstannanes Table

Pd/PCy(pyrrolidinyl)2 proved to be effective for room-temperature cross-couplings of an array of primary alkyl bromides and iodides with both vinyl- and arylstannanes (Table 6, entries 4-10). These examples establish that the desired carbon-carbon bond formation proceeds in the presence of functional groups such as cyanides (entry 5), esters (entries 5,7, and 8), and pyridines (entry 9). 

One of the first papers dealing with Pd-catalyzed homocoupling of alkenylstannanes utilized f-butylhydroperoxide as an oxidant. The reaction gave good yields of the corresponding dimers however, in some cases, stereochanistry of the double bond was lost. It was also demonstrated that this methodology is suitable for the homocoupling of arylstannanes (Table T)P ... 

Table 2 Reaction of arylstannanes with metal electrophiles...

Aryl ketones can also be prepared by C-acylation of support-bound arylstannanes with acyl halides (Entry 4, Table 12.1). The reaction conditions are mild and suitable for selective chemical transformations of polystyrene-bound intermediates. As an alternative, resin-bound arylstannanes can be converted into benzophenones by treatment with aryl halides and carbon monoxide ([(Pd(PPh3)4], DMSO, 80 °C, 18 h-3 d [8]). 

TABLE 2. Radial growth inhibition data of arylstannanes (ED50, mgl , errors given in paren-thesis)a73 74... 

Table 6 Stille couplings of alkyl bromides and iodides with vinyl- and arylstannanes...

Table 5. The yields of arylstannanes in the palladium-catalysed coupling of aryl bromides with hexamethyldistannane [99]...

However, aryl triflates have been coupled with arylstannanes in even less polar solvents in the absence of LiCl. The reactions of arylstannane 192 with pyridyl-2-sulfonates 193a-c furnish the corresponding 2,2 -bipyridines 194 and 195 in moderate to good yields, whereas the amount of the homo-coupling products derived from the parent arylstannane decreases in order Ar-OMs > Ar-OTs > ArOTf [83], Table 8. 

The Sn-NMR chemical shifts of the poly(alkyl-) and poly(arylstannanes), surprisingly, are quite similar the cyclic products have up field chemical shifts (Table 8.1). In contrast to the fairly linear polystannanes prepared by the catalytic action of zirconocene catalysts, branched polymers are obtained in the reaction of Bu2SnH2 with the rho-... 

Tributyltin hydride-mediated hydrodebromination of bromoarenes is selectively carried out. However, removal of the tin residue should be carefully carried out. The 10% w/w anhydrous potassium carbonate-silica repeatedly reduces organotin impurity levels below 15 ppm in this system (Table 3-12). In addition, organotin reagents such as tributyltin hydride, allyl stannanes, vinyl stannanes, arylstannanes, and distannanes can be purified by the K2CO3 and silica column chromatography. On the contraiy, halostannanes and sulfonated stannanes are trapped through this process (Table 3-13). 

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