Tributyltin methoxide

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]. 

Note. Enol acetates undergo a similar oxidation, using the palladium species and tributyltin methoxide as dual catalysts. 

The reduction of tributyltin methoxide with optically active methyl-phenyl-1-naphthylsilane involves retention of configuration at the silicon atom and follows second-order kinetics (2 72). The reaction between tributyltin methoxide and ring-substituted dimethylphenylsilanes shows a Hammett p-value of -t-0.903, and that between dimethyl-phenylsilane and ring-substituted tributyltin phenoxides shows a p-value of -1.319 this is compatible with the reactions proceeding through a 4-centered (SNi-Si) transition state (272, 173). 

Dimethyltin dichloride (hRf 15-20), trimethyltin chloride (h/ f 55-60), dibutyltin dichloride (h/ f 70-75) and tributyltin methoxide (h/ f 80-85) appeared in long-wavelength UV light (X = 365 nm) as yellow fluorescent chromatogram zones on a dark background. The detection limits (calculated as Sn) lay between 5 and 10 ng (dimethyltin dichloride, dibutyltin dichloride, tributyltin methoxide) and 50 ng (trimethyltin chloride) substance per chromatogram zone. 

Fig. 1 Fluorescence scan of a chromatogram track with 100 ng substance (calculated as Sn) each per chromatogram zone 1 = dimethyltin dichloride, 2 = trimethyltin chloride, 3 = dibutyltin dichloride, 4 = tributyltin methoxide.

Tributyltin chloride la 399,400 Tributyltin methoxide lb 319 Tributyltin oxide la 399,400 Tricarboxylic acids la 248,249 Trichloroacetic acid la 45 -, reagent la 372,420... 

This was prepared from the diol 20 (eluant chloroform), yields 77% (A) and 87% (B) as a syrup (film) 1740 (CO) and 3500 cm-1 (OH). When either molecular sieves or tributyltin methoxide were omitted, the yield dropped to 37% [27]. 

Yamamoto has recently described a novel catalytic, asymmetric aldol addition reaction of enol stannanes 19 and 21 with aldehydes (Eqs. 8B2.6 and 8B2.7) [14]. The stannyl ketones are prepared solvent-free by treatment of the corresponding enol acetates with tributyltin methoxide. Although, in general, these enolates are known to exist as mixtures of C- and 0-bound tautomers, it is reported that the mixture may be utilized in the catalytic process. The complexes Yamamoto utilized in this unprecedented process are noteworthy in their novelty as catalysts for catalytic C-C bond-forming reactions. The active complex is generated upon treatment of Ag(OTf) with (R)-BINAP in THF. Under optimal conditions, 10 mol % catalyst 20 effects the addition of enol stannanes with benzaldehyde, hydrocinnamaldehyde, or cinnamaldehyde to give the adducts of acetone, rerf-butyl methyl ketone (pinacolone), and acetophenone in good yields and 41-95% ee (Table 8B2.3). 

The tributyltin alkoxides (Table VI) also show high-frequency chemical shifts, independent of the nature of the alkoxy substituent, and are thus monomeric tetrahedral species in the neat liquid at room temperature. At 80 K, however, both tributyltin methoxide and phenoxide are self-associated. (63)... 

Glycosyl acetates react with tributyltin methoxide to give glycosyl tributylstannyl ethers. As with glycosyl anions,337"339 the anomeric effect causes... 

In a similar way4, treatment of 3-methyl-2-oxetanone 2 (R = CH3) with tributyltin methoxide and phenyl isocyanate leads to methyl (aR,55)-a-methyl-2-oxo-3-phenyl-5-oxazolidineacetate (9, R = CH3) in 71% yield. 

Addition polymerisation of nitriles using organotin catalysts like tributyltin methoxide at 333-403 K > ). 

The tributyltin enolates 74 are readily prepared from the corresponding enol acetates and tributyltin methoxide in the absence of solvent [34]. The tin enolates thus obtained occur in the 0-Sn form and/or the C-Sn form, and both species can be used for the aldol reaction of this system. Although the tin enolates themselves have adequate reactivity toward aldehydes [34c], in the presence of the BINAP silver(I) catalyst the reaction proceeds much faster even at -20 °C. Optimum conditions entail the use of THF as solvent and the results employing these conditions in the catalytic enan-tioselective aldol reaction of a variety of tributyltin enolates with typical aromatic, a,/3-unsaturated, and aliphatic aldehydes are summarized in Table 2. TTie characteristic features are (i) All reactions proceed to furnish the corresponding aldol adducts 75 in moderate to high yield in the presence of 10 mol % (i )-BINAP AgOTf complex at -20 °C for 8 h, and no dehydrated aldol adduct is observed (ii) with an a,j3-unsaturated aldehyde, the 1,2-addition reaction takes place exclusively (entry 3) (iii) a bulky alkyl substituent of tin enolate increases the enantioselectivity of the aldol reaction. For instance, the highest ee (95 % ee) is obtained when the tin enolate prepared from pinacolone 77 or rert-butyl ethyl ketone 79 is added to aldehydes (entries 2, 7, and 8) (iv) addition of the cyclohexanone-derived enol tributylstannane 78 (( )-... 

The phosgenation of the tributyltin enolate of acetone led to the same results although some trials performed at low temperature (below - 20°C) showed the possibility to obtain small amounts of isopropenyl chloroformate. It is noteworthy that, in a recent work devoted to a new synthesis of retinal (Vitamin A aldehyde), Bienayme from Rhone-Poulenc (Ref. 117), obtained isopropen-1-yI chloroformate in low yield through phosgenation of the reaction product of tributyltin methoxide with 1-acetoxy isoprene as depicted in scheme 92. 

Analogous carbonyl-forming eliminations occur with the adducts formed between organotin oxides or alkoxides and trihalogenomethyl aldehydes or ketones, and tributyl-trichloromethyltin was first prepared by the elimination of methyl trichloroacetate from the adduct of tributyltin methoxide and hexachloroacetone.135 136... 

Examples of addition reactions of tributyltin methoxide are given in Table 14-3. Most of these reactions are reversible for example, the alkyl tin carbonate which is formed by the addition of a tin alkoxide to carbon dioxide eliminates C02 on heating to regenerate the tin alkoxide (equation 14-14). Again, the product of the reaction of an acyl halide with a dioxastannolane is involved in an exchange reaction in which the tin alkoxide adds reversibly to the carbonyl group (equation 14-31).41... 

The reaction of tributyltin methoxide with hexachloroacetone to give tributyl(tri-chloromethyl)tin (Section 6.1) involves an addition followed by a 1,2-elimination reaction. 

A number of methods are now available for preparing the tin enolates, which are often not isolated, but are generated and caused to react further in situ. Tributyltin methoxide reacts exothermically with enol acetates without a solvent, to give the corresponding stannyl enolate, and methyl acetate which can be removed under reduced pressure or by slow distillation (b.p. 57 °C) (e.g. equation I4-54).37-104-105... 

Bis(tributyltin) enediolates can be prepared from the reaction of acyloins with bis(tributyltin) oxide or tributyltin methoxide (equation 14-61).112... 

The reaction of less electrophilic halides, particularly aryl and vinyl halides, can be catalysed with a palladium compound (equations 14-63 and 14-64),115 and the tin enolate can be prepared in situ from the enol acetate and tributyltin methoxide, or lithium enolate and tributyltin trifluoroacetate, or silyl enolate and tributyltin fluoride. 

Whereas alkoxystannanes can be prepared by azeotropic dehydration of a mixture of bis(tributyltin) oxide and an alcohol (pKa ca. 16), aminotin compounds cannot normally be prepared from the oxide and an amine (pKa ca. 35). The important exception to this rule is pyrrole which is a stronger acid (pKa 15), and iV-tributylstannylpyrrole can readily be prepared by the azeotropic dehydration of bis(tributyltin) oxide and pyrrole, or by heating together tributyltin methoxide and pyrrole.3... 

Debenzoylation must be carried out under mild conditions, since the 2-alkoxide ion can attack the oxetane ring to form a new tetrahydrofuran ring. Thus treatment of 7,13-diacetylbaccatin III with tributyltin methoxide gave the rearranged product 3.4.5 109), and treatment of 7-(triethylsilyl)-10-deacetylbaccatin III with base gives a similar product (109). 

Not only silyl end ethers but also enol acetates prepared from saturated ketones give a,/3-unsaturated ketones by heating with allyl methyl carbonate in the presence of Pd(II)(OAc)2 and dppe with tributyltin methoxide as a bimetallic catalyst (Scheme 12). Regioselective generation of palladium(II) enolate intermediate is simply carried out by treatment of allyl enol carbonates, which are prepared by trapping of ketone enolates with chloroformate, with Pd(II)(OAc)2 in the presence of dppe (Scheme 13). 7r-Allylpal-ladium(II) enolates thus generated provide a,/3-nnsatnrated ketones. 

Tributyltin acetate, see Sn-00289 >Tributyltin chloride, see Sn-00252 >Tributyltin hydride, see Sn-00258 Tributyltin isocyanate, see Sn-00278 Tributyltin methoxide, see Sn-00279 Tributyltin methylthiolate, see Sn-00280 Tributylvinylstannane, Sn-00290 Tricarbonyl(7 -benzyltrimethylstannane)chromium, see Sn-00273... 

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