Thallium ethoxide

The presence of three hydroxyl groups per glucose unit was shown by the preparation of a triacetate and a tribenzoate. Six or seven methyla-tions (using dimethyl sulfate and concentrated alkali) of dextran did not raise the methoxyl content above 41% (theoretical maximum 45.6%). Also, Purdie methylations (using methyl iodide and silver oxide) and methylation with thallium ethoxide and methyl iodide were ineffective in raising the methoxyl content of methylated dextran above 43.5%. The maximum theoretical methoxyl content was eventually attained by modified Muskat methylations. 6 Partially methylated dextran suspended in anisole solution was treated with sodium in liquid ammonia, and the sodium salt of methylated dextran thus formed was allowed to react with methyl iodide. The methoxyl content of the partially methylated dextran was raised by three such methylations from 42% to 45.5% and by five such methylations from 30% to 45.4%. 

In the first step a selected Schiff base (3 mmol) was dissolved in 15 ml THF and then added dropwise to a solution of thallium ethoxide in 5 ml THF at ambient temperature. Immediately after the addition, a pale yellow solid formed the reaction mixture was stirred for 2 hours at 20°C and then used immediately. 

The heterocycles react directly with alkali metals or undergo exchange reactions with, for example, sodium amide and hydride, n-butyllithium and thallium ethoxide, to form the TV-heteroaryl salts. The salts of the alkali metals exist as solvent separated ion-pairs or as contact ion-pairs (71JOC3091), as do the quaternary ammonium salts, whereas the salts of the heavier metals are generally considered to have a high N—metal covalent character. These characteristics, which can be modified by a change in the polarity of the solvent, control the reactions of the heteroaryl anions. 

A compound formulated as 5-methyl-1,4-dihydro-1,2,4-triazin-3(2//)-one (696) was obtained by sodium hydroxide treatment of compound (697). Reacting (697) with thallium ethoxide led to the isolation of diethyl 5-methyl-3-oxo-l,2,3,4-tetrahydro-l,2,4-triazine-1,6-dicarboxylate (698) (70JOC3792). Since compound (697) is formed by reaction of aminocrotonic ester with diethyl azodicarboxylate, these reactions can also be treated as [3 + 3] atom component preparations. 

In a first approximation supra-Cp metal complexes can be prepared the same way as normal or other Cp-metal and organo-metal bonds in general. The methods used most often (see Appendix) are the metathesis reaction [Eq. (1)] followed in number by oxidative additions (Eq. (2)] and metallation/deprotonation reactions [Eq. (3)]. The latter is especially important for the cyclpentadienyl alkali metal compounds. A useful variation of reaction (3) is the formation of CpTl in an acid/base reaction from cyclopentadiene and thallium ethoxide [Eq. (3b)]. This represents a convenient route to cyclopentadienylthallium compounds, which are also valued (in place of Cp alkalis) as mild Cp-transfer reagents for the synthesis of difficultly isolable cyclopentadienyl derivatives (77). 

The final conditions which we found consistently to give a quantitative analysis for carboxylic acids are shown in the Figure 10. Neat thallium ethoxide is a clear, not very viscous or volatile liquid at room temperature and pressure. Simple immersion of the polymer in this tetramer causes rapid penetration and reaction. Excess reagent can be washed out easily with ethanol to leave the thallium label behind. To remove excess ethanol, the sample was left in the vacuum prechamber for 30 minutes before measurement. Some excess oxygen is still seen. The samples are stable and have been found to keep the same thallium level even after being in the spectrometer under X-rays for more than an hour. Much less time is needed for analysis since the cross section is about 12 times that of C(ls). Carboxylic acid salts of thallium are known to be very stable to air, moisture and light (14). Preliminary experiments on an analogous mixed acid/ester system show that the ester functionality is not labeled, while the acid is. 

Clearly, neat thallium ethoxide and dilute sodium hydroxide can be used to tag carboxylic groups on polymer surfaces so they can be meausred by ESCA. Correct interpretation of the results is aided by understanding the kinetics of each surface reaction. 

The conditions involving dichlorocarbene generated from chloroform and thallium ethoxide give the best chemoselectivity, yields and reproducibility (Scheme 162, e Scheme 16S, c Scheme 166, e Scheme 186, b Scheme 188, a Scheme 189, The reactions are usually carried out at... 

Procedures which utilize selenides are similar, but a-lithio selenides are not generally preparable via simple deprotonation chemistry, due to facile selenium-lithium exchange. - Selenium-stabilized anions are available, however, by transmetalladon reactions of selenium acetals and add readily to carbonyl compounds. The use of branched selenium-stabilized anions has been shown to result exclusively in 1,2-addidon to unhindered cyclohexenones, in contrast to the analogous sulfur ylides. The resulting 3-hydroxy selenides undergo elimination by treatment with base after activation by alkylation or oxidation (Scheme 10). An alternative method of activating either p-hydroxy selenides or sulfides toward elimination involves treatment of a chloroform solution of the adduct with thallium ethoxide (Scheme 11). A mechanism involving the intermediacy of a selenium ylide is proposed. 

These reactions have been used for the synthesis of cuparenones from p-methoxyacetophenone 135) (Scheme 98) and for the synthesis of permethylcyclo-pentanone, permethylcyclohexanone, and of permethylcyclohexane from acetone 224) (Scheme 99). If the carbon bearing the selenenyl moiety bears at least one hydrogen, reaction of thallium ethoxide in chloroform is described to lead instead to epoxides42 , and this was found to be the case234 for P-selenocylobutanols (Scheme 101). Closely related results have been observed when the reactions are performed under phase transfer catalysis simply with chloroform and potassium hydroxide as the dihalocarbene sources 235). 

There has been considerable activity in the synthesis of orsellinic acids in the past decade. On account of their ready decarboxylation all these procedures also give access to 5-alkylresorcinols. These routes are summarised in the scheme shown. Homologous alkyl acetoacetates (R = R = alkyl) with thallium ethoxide or sodium hydride followed by reaction with diketene (route a) afford the corresponding homologous alkyl orsellinates (ref.23). In a related method (route b) methyl orsellinate (R = Me) results from the interaction of the monoanion with the dianion of methyl acetoacetate (ref.24). 

Chiral crown ether derived from L- (+)-tartaric acid. French chemists have prepared the chiral crown ether (1) from L-(+)-tartaric acid using the new etherification procedure of Crass et al. (see Thallium ethoxide, this volume). 

Taylor and co-workers found that the Michael additions of diethyl azodi-carboxylate to the enaminones 663 gave the derivatives 664, which were cyclized with thallium ethoxide to the as-triazinones 665 in almost quantitative yields. Cyclization of 664 was also effected with aqueous sodium hydroxide, but under these conditions concomitant hydrolysis and decarboxylation occurred to give the triazinone 666. The cyclization of the enaminone 664 (R = NH2, = H) failed under basic conditions, but treatment with bromine and diisopropylethylamine smoothly afforded the triazine 667, Scheme 184 (70JOC3792). 

A variant of the Williamson reaction for the preparation of ethers utilizes thallium ethoxide to convert the vicinal hydroxy groups in tartaric esters to the thallium(I) oxide derivative 590, which upon treatment with alkyl halides provides excellent yields of dialkylated tartaric esters 569 [189]. 

Conversion of lb to the dimethylamide 591 [190] and introduction of thallium ethoxide followed by treatment with an appropriate alkyl halide generates in good to excellent yield the di-O-alkylated tartaramides 592 [189]. 

Black, crystalline. Begins to volatilize In high vacuum at 300°C. B.p. at least 1080°C. Hygroscopic reacts with water, forming TlOH for solubility in water see TlOH. Solubility in absolute ethanol at room temperature 4.4 mg. TlOg/lOO ml. alcohol heating produces thallium ethoxide. d 9.52. 

Lamy reports that hydrolysis of thallium ethoxide precipitates TlOH. Thallium ethoxide can be rapidly prepared by the Fricke... 

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