Tributyltin , structure

The most important of the compounds from an ecotoxicological point of view, and the one that will be used here as an example, is tributyltin oxide (TBTO). Its structure is shown in Figure 8.5. 

TBTO is a colorless liquid of low water solubility and low polarity. Its water solubility varies between <1.0 and >100 mg/L, depending on the pH, temperature, and presence of other anions. These other anions determine the speciation of tributyltin in natural waters. Thus, in sea water, TBT exists largely as hydroxide, chloride, and carbonate, the structures of which are given in Figure 8.5. At pH values below 7.0, the predominant forms are the chloride and the protonated hydroxide at pH8 they are the chloride, hydroxide, and carbonate and at pH values above 10 they are the hydroxide and the carbonate (EHC 116). 

Zard and coworkers [32] reported a simple approach to create another group of natural products, namely the lycopodium alkaloids [15]. These authors first investigated the reaction of O-benzoyl-N-allylhydroxylamide 3-60 with tributyltin hydride and ACCN in refluxing toluene, which led (after formation of the N-radical 3-61 in a 5-exo-trig/5-exo-trig cyclization) to the undesired pyrrolidine 3-62 in 48% yield. Nevertheless, a small structural modification, namely the placement of a chlorine atom at the allyl moiety as in 3-63, induced a 5-exo-/G-endo- instead of the 5-exo-/5-... 

The [6.5.5]-ring fused tricyclic motif is found in many natural products, and has therefore become an important target in synthesis. A convenient access to this structural framework is offered by a radical domino procedure published by the Nagano group [41]. This reaction of optical pure dibromoacetal 3-85 led to the desired tricycle 3-87 via 3-86 as a single diastereoisomer in a very respectable yield of 94% by applying classical radical conditions (excess tributyltin hydride/AIBN, irradia-... 

Figure 8.1 Environmental degradation scheme tor tributyltin and triphenyltin compounds. (Modified from Smith, P.J. 1978b. Structure/Activity Relationships for Di- and Triorganotin Compounds. I.T.R.I. Rep. 569. 16 pp. Avail, from International Tin Research Institute, Greenford, Middlesex, U.K. and Eisler, R. 1989. Tin hazards to fish, wildlife, and invertebrates a synoptic review. U.S. Fish Wildl. Serv. Biol. Rep. 85(1.15). 83 pp.

Scadding, S.R. 1990. Effects of tributyltin oxide on the skeletal structures of developing and regenerating limbs of axolotyl larvae, Ambystoma mexicanum. Bull. Environ. Contam. Toxicol. 45 574-581. 

Certain organotins, such as di- -octyltin dichloride (DOTC) and tributyltin oxide (TBTO), alter the structure and function of the thymus and consequently affect pri-... 

In the solid state, the most common structure of the monocarboxylates, in the absence of any major steric demands, is that of a linear polymer 33, but tributyltin 2,6-difluorobenzoate forms a cyclic tetramer, (Bu3SnOCOAr)4.349... 

Since most of the above polymer compositions have tin anchored as tributyltin carboxylates, we have initiated a study of the structure and reactivity of tributyltin carboxylates. 

Our approach was to use the unsaturated bromodeoxylactones in an intramolecular radical reaction, since these compounds possess both the radical precursor and the radical trap within the same molecule. Thus, reacting the unsaturated bromodeoxyheptonolactone 20 (Scheme 14) with tributyltin hydride and a radical initiator, the bicyclic lactone 65 a was obtained in a quantitative yield within 1 h. The stereocontrol in the reaction was determined by the structure of the product, since the compound obtained has two fused cyclopentane rings which can only be cis anellated. The radical A, which is the intermediate, was trapped by the tin hydride. The stereochemistry of the newly formed chiral center is determined by the configuration at C-4 in the educt 20 [45]. 

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