Trialkylstannyl groups

Sulfones with a trimethylsilyl or trialkylstannyl group at the -position or at the -position are readily converted to olefins upon treatment with tetra-n-butylammonium fluoride in THF (equations 39-41). The method is compatible with the presence of a variety of functionalities. 

Sauer and Heldmann [97] recently reported an interesting application of ethynyltributyltin as an electron-rich dienophile in an inverse electron-demand Diels-Alder reaction with the electron-deficient triazine derivative 94. This method is interesting because the reaction is highly regioselective and the trialkylstannyl group is easily replaced by several groups under mild conditions, leading to substituted pyridines 95 (Scheme 2.41). 

In the spectra of the MA/TBSM mixture, the absorption band of the C = C bond is observed to shift to a shorter wavelength which indicates localization of electron density toward the trialkylstannyl group 2,19). 

The resulting values point to the fact that organotin monomer units enter the macromolecular chain. To reveal the contribution of trialkylstannyl groups to radical copolymerization, the copolymerization of their organic analogs (BMA and MA) with VC was investigated. 

Trialkylstannyl groups — e.g. tributylstannyl—resist reaction under conditions that affect other parts of organic molecules. This property may be useful for mechanistic and structural studies. 

Acetal ethers containing the trialkylstannyl group undergo the interesting rearrangement 77, catalysed by Ti(IV) compounds328. 

An example of the first type of reaction, where a trialkylstannyl group is replaced by an isotope of hydrogen, is shown in equation 91. In this example, methanolysis using methanol-O-D replaces the tributylstannyl group with a deuterium atom127 128. 

Trialkylstannyl groups can also be replaced by reactive electrophiles in certain cases, but most commonly stannylated azaheterocycles are employed in palladium catalyzed cross-coupling reactions [85PAC1771 86AG(E)508 92S413]. For example, trimethylstannylpyridines can be reacted with bromopyridines in the presence of catalytic amounts of tetrakis-(triphenylphosphine)palladium to give a variety of different bipyridines (Scheme 158)(86S564). 

It was anticipated that a C4 /1-trialkylstannyl group would intercept the C4 radical and result in loss of antimalarial activity. Indeed, 31 and 32 were inactive and iron(II) degradation afforded two major products in which the stannyl group had been eliminated (Scheme 6). They proposed that the deoxo derivative 33 was produced by elimination of a... 

The data in Table 3-1 indicate that a trialkylstannyl group should have only a weak electron attracting or electron releasing effect whatever the skeleton the group is attached to, or the phenomenon which is being studied. 

Reactions of 2-trialkylsilyl- and trialkylstannyl-substituted furans with benzhydryl cations provided 2,5-disubstituted furans and ipso-substituted furans. Kinetic investigations of the reactions revealed that the monosubstituted product was produced from the protonolysis of the 2,5-disubstituted furylstannane, while the 2,5-disubstituted furan was derived from an electrophilic substitution of the mono-substituted furan. Introduction of a trialkylsilyl and a trialkylstannyl group to the 2-position of furan hardly affected the reactivity of this position towards carbenium ions ipso attack), while the 5-position is somewhat activated <01OL1629,01OL1633>. 

---