Trimethyltin halides reactions

Trimethyltin halides are fairly soluble in water, and can often be washed out of a solution of the reaction mixture in an immiscible solvent. If the desired product is polar, it can be separated from tributyltin halides by partition between acetonitrile and hexanes, which are immiscible.52 53... 

We note that while tin reagents have often been employed for the organoboron halides/ the use of organostannanes as starting materials can also be applied to the synthesis of heavier group 13 derivatives. In the context of polyfunc-tional Lewis acid chemistry, this type of reaction has been employed for the preparation of ort/ o-phenylene aluminum derivatives. Thus, the reaction of 1,2-bis(trimethylstannyl)benzene 7 with dimethylaluminum chloride, methylaluminum dichloride or aluminum trichloride affords l,2-bis(dimethylaluminum)phenylene 37, l,2-bis(chloro(methyl)aluminum)phenylene 38 and 1,2-bis(dichloroalumi-num)phenylene 39, respectively (Scheme 16). Unfortunately, these compounds could not be crystallized and their identities have been inferred from NMR data only. In the case of 39, the aluminum derivative could not be separated from trimethyltin chloride with which it reportedly forms a polymeric ion pair consisting of trimethylstannyl cations and bis(trichloroaluminate) anions 40. 

Cyanamides are pseudo-halide nitrogen ligands that are readily coordinated to metals. A novel compound is 2-cyanaminofluoren-9-one (HL4)24. Its thallium salt T1+(L4)-(Scheme 7) is useful as a transmetallating agent in a reaction with trimethyltin chloride to produce the corresponding tin cyanamide complex [SnMe3L4] (Scheme 8). 

The resin-bound trialkyltin halide developed for this reaction required higher catalytic loadings (30-100%) to obtain reasonable yields of coupled product, (Scheme 5.8.12), presumably reflecting the availability of the catalytic site in the biphasic mixture. Tin contamination of the column purified product, however, was <5-60 ppm compared with >500 ppm obtained for the free trimethyltin chloride-catalyzed reaction. 

It is interesting to note that Ashby s investigations of the reactions of alkyl halides with (trimethyltin)sodium and dialkylcuprates by means of the l-methyl-5-hexenyl probe which led to the conclusion that only radicals cyclize 98), have been questioned by Lee and San Fillipo in 1983 " . These authors correctly state that the cyclization alone does not prove a radical pathway. The cis/trans ratios from reactions of the halides 136 with (trimethyltin)sodium (revised 4.8 at 0 °C)96 , however, are consistent with 100% radical cyclization. 

The Stille coupling reaction is the most versatile method among all Pd-catalyzed crosscoupling reactions with organometallic reagents. By lithiation of 4-methyloxazole with H-BuLi and subsequent quenching with trimethyltin chloride, Dondoni et al. prepared 2-trimethylstannyl-4-methyloxazole [39], which was then coupled with aryl- and heteroaryl-halides to provide the expected 2-aryloxazole. Thus, 2-trimethylstannyl-4-methyloxazole was coupled with 3-bromo-pyridine to afford oxazolylpyridine 35. 

Very similar reactions are also undergone by compounds containing a Sn-Sn bond thus trifluoromethyl(trimethyl)tin and trimethyltin iodide are formed when hexamethylditin and trifluoroiodomethane are heated in a Carius tube 421 and dibutyltin and alkyl halides afford alkyldibutyltin halides.422... 

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