Tributyltin fluoride

Tin enolates of ketones can be generated by the reaction of the enol acetate 733 with tributyltin methoxide[60i] and they react with alkenyl halides via transmetallation to give 734. This reaction offers a useful method for the introduction of an aryl or alkenyl group at the o-carbon of ketones[602]. Tin enolates are also generated by the reaction of siiyl enol ethers with tributyltin fluoride and used for coupling with halides[603]. 

In more recent years two new types of antifouling composition have been developed, using organometallic compounds as poisons. In one type, based chiefly on vinyl resin and organotin compounds (e.g. tributyltin fluoride), the poison and resin form a solid solution. As the poison dissolves from the surface of the film, more poison diffuses from deeper in the film to... 

A chloroform solution of toxic tributyltin fluoride was placed in a round-bottomed flask equipped with a reflux condenser, and bromine (3 equiv per Bu3SnF) was added all at once. After the mixture was stirred for 2-3 days at room temperature, aqueous sodium thiosulfate was added until the brown color of bromine disappeared. The aqueous layer containing inorganic tin compounds.was disposed of in accordance with Prudent Practices for Disposal of Chemicals from Laboratories" National Academic Press Washington, DC, 1983. 

Marine antifouling paints containing tributyltin oxide or tributyltin fluoride are widely used all over the world29. However, tributyltin from marine antifouling paints has been shown to have a major impact on the oyster industry in Australia and in France. Concern for these effects has now led to the banning in many countries of the use of tributyltin-based antifouling paints on pleasure boats35. 

As depicted in Scheme 3-25, the aldol reaction carried out at —78°C can give the corresponding aldol adduct 72 in 78% yield with 82% ee. The combination of chiral diamine-coordinated tin(II) triflate and tributyltin fluoride is so essential that the enantioselectivity cannot be obtained without tributyltin flu-... 

Although in the recent years the stereochemical control of aldol condensations has reached a level of efficiency which allows enantioselective syntheses of very complex compounds containing many asymmetric centres, the situation is still far from what one would consider "ideal". In the first place, the requirement of a substituent at the a-position of the enolate in order to achieve good stereoselection is a limitation which, however, can be overcome by using temporary bulky groups (such as alkylthio ethers, for instance). On the other hand, the ( )-enolates, which are necessary for the preparation of 2,3-anti aldols, are not so easily prepared as the (Z)-enolates and furthermore, they do not show selectivities as good as in the case of the (Z)-enolates. Finally, although elements other than boron -such as zirconium [30] and titanium [31]- have been also used succesfully much work remains to be done in the area of catalysis. In this context, the work of Mukaiyama and Kobayashi [32a,b,c] on asymmetric aldol reactions of silyl enol ethers with aldehydes promoted by tributyltin fluoride and a chiral diamine coordinated to tin(II) triflate... 

Table 9.6 shows the effect of both the addition time and the polarity of the solvent, as well as the nature of the aldehyde, in the catalytic asymmetric aldol condensation promoted by tributyltin fluoride and a chiral diamine coordinated to tin(n) triflate. 

ANTIFOULING AGENTS. Various chemical substances added to paints and coatings to combat mildew and crustaceous formations, such as barnacles on the hull of a ship. In the past, large quantities of mercury compounds have been used in this manner. With growing environmental concern over possible mercury pollution, manufacturers have been turning to other, sometimes less efficacious compounds, Research continues to find compounds of a less toxic, but equally effective power of the mercury compounds. Bis(tributyltin) fluoride has been used on ship bottoms. See also Mercury. 

Animal studies tend to confirm the dermal/ocular effects reported for humans. Bis(tributyltin)oxide is a severe irritant to the skin and an extreme eye irritant in rabbits (Sheldon 1975). By contrast, tributyltin fluoride and triphenyltin fluoride produced only minimal skin irritation but were also extreme eye irritants (Sheldon 1975). Other acute studies have likewise demonstrated the skin irritating potential of bis(tributyltin)oxide and triphenyltin acetate in rats (Klimmer 1969 Pelikan and Cerny 1968). 

In a 90-day repeated dose dermal study, rabbits developed skin irritation at each of three levels tested (14, 27, and 68 mg/kg/day tributyltin fluoride) (Sheldon 1975). Deaths occurred in 7 of 10 rabbits at a level of 68 mg/kg, but surviving animals eventually returned to normal a few days after compound was withdrawn. A level of 14 mg/kg (65 applications) was stated by the authors to be a NOAEL despite local irritation at the application sites. In view of the exaggerated daily contact with the rabbit skin, this value seems reasonable since such high levels of daily exposure would not be the case in humans. However, a detailed report of this study was not available for review. 

In a limited evaluation of carcinogenicity, tributyltin fluoride was applied to the shaved backs of male white mice 3 times per week for a period of 6 months. Treated mice received 15 mg of 5% or 10% of the compound in propylene glycol. Hyperplastic skin changes were observed in the 5% but not in the 10% group (Sheldon 1975). Carcinogenic effects were not observed in this study, which was only of intermediate duration. No other studies were located regarding cancer effects in animals after dermal exposure to organotin compounds. 

It has been reported that low concentrations of tributyltin fluoride were readily transformed to tributyltin chloride in sea water (Strand 1983). Tributyltin has been shown to undergo slow photolysis (Maguire et al. 1983). The half-life of the photolysis reaction was estimated to be greater than 89 days. The direct photolysis of tributyltin in water initiates a sequential removal of the butyl groups, leading to inorganic tin as a residual. The reaction was much faster in the presence of fulvic acid (a major component of soil organic matter). 

Asymmetric aldol-type reactions.1 This chiral diamine (1) in combination with tin(II) triflate and tributyltin fluoride (15, 314-315) effects a highly enantioselective aldol-type reaction between ketene silyl acetals and aldehydes. A tentative structure (2) has been suggested for the promotor. 

The initial filtration with silica gel is necessary to remove most of the tributyltin fluoride. 

In most cases the trimethyl tin reagents are preferred since the byproduct. trimethyltin chloride, can easily be removed by water extraction. In the case of the water-insoluble tributyltin chloride it is necessary to add an aqueous solution of potassium fluoride to an ethereal solution of the product thereby forming insoluble tributyltin fluoride, which can be separated by... 

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