Dialkyltin oxide

Hydrolysis of compounds R2SnX2 gives the dialkyltin oxide via a number of intermediates (Scheme 15). 

The difunctional distannoxanes XR2SnOSnR2X can also be prepared from the reaction of (R2SnO) with R2SnX2, or from (R2SnO) and the appropriate amount of the acid HX. A further alternative is to heat the dialkyltin oxide with saturated aqueous NH4X (X = F, Cl, Br, I, OAc) in refluxing dioxane, and this probably provides the best route to the fluorides FR2SnOSnR2F.331... 

The 1,3,2-dioxastannolanes are important in organic synthesis because they can readily be derived from dialkyltin oxide and 1,2-diols, as in carbohydrates the reaction can be carried out in toluene in a few minutes under microwave irradiation.387 The dioxastannolanes can then be subjected to regioselective reaction with an electrophile such as an acyl chloride (Equation (140)) or sulfonyl chloride, or an isocyanate. The acylation or sulfonation can be carried out with catalytic amounts of the dialkyltin oxide, including the recoverable (C6F13CH2CH2)2Sn0.388... 

Unsaturated tin(IV) derivatives, 2,2-dialkyl-l,3,2-dioxastannoles (348), undergo a telomerization reaction with dialkyltin oxide to give a set of cyclic oligomers (349) <82JOM(224)C37, 83JOM(25l)203>. This telomerization can be combined with the synthesis of 2,2-dialkyl-1,3,2-dioxastannoles (Scheme 35). 

Dibutyltin oxide, dibutyltin dimethoxide, and hexabutyldistannoxane are commercially available. Di-f-butyltin dichloride is commercially available, but reactions of di-f-butylstannylene acetals are often very slow. In certain cases, there are advantages in using bulkier tin oxides or tin oxides that are sterically restricted, such as cyclic tin oxides.19,20 Non-commercial dialkyltin oxides may be prepared conveniently by the reaction of dialkyldiphenyltin with chloroacetic acid followed by sodium hydroxide.21 This procedure works well for the preparation of stannacycloalkanes as well as bulky dialkyltin oxides. 

The activation is carried out by reaction of the polyol with bis(trialkyltin) oxide or a dialkyltin oxide with heating and can be performed in various solvents, the most common being methanol... 

The polycondensation of BHET to PET proceeds in the melt at temperatures of 270-305 °C, under vacuum (< 1 mbar absolute pressure) and in the presence of Lewis acid metal compounds, such as titanium alkoxides, dialkyltin oxide, gallium oxide, germanium oxide, thallium oxide, lanthanide salts, and most commonly, antimony oxide [1,2, 22-26]. Under polymerization reaction conditions, these catalysts are generally converted to their alkoxides with ethylene glycol. Typical of such alkoxides is antimony(III) glycolate, the active catalyst for the majority of the world s PET production [27] (cf. Structure 1). 

The compounds (61 R = Me or Bu X = CMe2CH2CHMe, CMe2CMe2, or CHMeCH2) have been prepared from the dialkyltin oxide, H3B03, and the... 

The exchange reaction between the Sn-O bond in dialkyltin oxides, R2SnO, and the SnCl bond in organotin halides is discussed in Section 12.4. 

Under these conditions, dialkyltin oxides react to form only the dialkoxy-distannoxanes, though if these are heated at about 200 °C under reduced pressure, the dialkyltin dialkoxide can be distilled off, leaving a residue of the dialkyltin oxide.1 In tetrahydronaphthalene (b.p. 207 °C), however, phenols give the dialkyltin diphenoxides directly.4... 

Two types of tin derivatives have been used mainly to achieve these reactions dialkylstannylene acetals are formed by reaction of dialkyltin oxides with diols tributyltin ethers are formed by reaction of bis(tributyltin) oxide with alcohols. Some aspects of the regioselectivity achieved with these two types of intermediates are the same, while others are different, as will be outlined in the sections to follow. Where the reaction outcomes are similar, the dialkyltin reagents are strongly preferred because of their lower toxicity. As these reagents are heavily employed, the topic has been reviewed several times, but siguilicant uew observatious continue to be made. This chapter is not intended to be a comprehensive summary of all applicatious of these intermediates, but will highlight examples of each type of selectivity. 

Scheme 5.1.4 A general synthetic method for the preparation of dialkyltin oxides. Examples of XR used include /CHiCHiCsUa/ BrCH2CH(CH3)2/ BrCH(CH3)2, Br(CH2)eBi ...

The formal tin counterpart of the dioxolanes formed from vicinal diols by reaction with ketones are stannylenes, formed by reaction with dialkyltin oxides. The commonest reagent is dibutyltin oxide, Bu2SnO, which converts diols to stannylenes when refluxed in an aprotic solvent such as benzene, with continuous distillation out of the water generated. The partly ionic nature of... 

Dialkyl aminoethyl acrylic esters are readily prepared by transesterification of the corresponding dialkylaminoethanol (102,103). Catalysts include strong acids and tetraalkyl titanates for higher alkyl esters and titanates, sodium phenoxides, magnesium alkoxides, and dialkyltin oxides, as well as titanium and zirconium chelates, for the preparation of functional esters. Because of loss of catalyst activity during the reaction, incremental or continuous additions may be required to maintain an adequate reaction rate. 

High molecular weight polyesters can be obtained only with special techniques because of the difficulty of obtaining complete water removal without loss of monomers. The reaction is self-catalyzed by carboxyl groups and can be catalyzed by other acids, for example, -toluenesulfonic acid and by compounds such as titanium alkoxides, dialkyltin oxides, and antimony pentafluoride. 

Dialkyltin Compounds. All of the dialkyltin dimercaptides and dicarboxylates were prepared by reaction of the appropriate dialkyltin oxide (Alfa Inorganics) with the desired mercaptan or carboxylic acid. The reactions were carried out in refluxing benzene or toluene using a Dean-Stark water separator. The yields are quantitative and products require no purification (purity confirmed by H and 13C NMR). The dialkyltin dichlorides were obtained commercially (Alfa Inorganics) and used as received ... 

Short-chain group-IVB products analogous to polysiloxanes can be formed from the hydrolysis of the dihaloorganometallic monomer . The reaction of dialkyltin oxide with R2Si(OH)2 results in mixed polystannosiloxanes ... 

The dialkyltin oxides, R2SnO, are beheved to be network coordination polymers with 5-coordinate tin atoms [137, 184, 185], and the effect of the structure on the recoil-free fraction has been discussed. 

If mixed tin stabilisers are believed to be present, for example, a thio-compound and a dialkyltin dialkylcarboxylate, it is advantageons to acidify the acetone filtrate after removal of the dialkyltin oxides with hydrochloric acid, evaporate most of the acetone on a water-bath under an air-jet, cool and extract by shaking with diethyl ether. The ether extract then contains hemiesters, acids, and so on, liberated from the other types of tin stabilisers originally present and can be examined further. Although reaction products produced by... 

Metals of groups III-VI (namely Ti, Sb, Ge, Bi), usually introduced as alkoxides, dialkyltin oxides R2SnO and carboxylates such as dibutyltin dilaurate, coordinate with the acylic oxygen of esters. 

To filtrate A add a slight excess of concentrated hydrochloric acid (about 1 cm ) to precipitate the excess of silver ions as silver chloride. Shake the mixture well, allow to settle and filter through a Whatman No. 541 filter paper. Make the filtrate alkaline by the addition of 25 cm of 10 per cent sodium hydroxide solution and again shake and filter through a Whatman No. 541 filter paper, this time washing well wifii acetone. Dry at 105°C for 30 mins. This gives a crude sample of the dialkyltin oxide but this is sufficiently pure for identification by infirared spectrophotometric examination (potassium bromide). 

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