And Williamson reaction

Methoxythiazole has been prepared by the Williamson reaction. The methoxy group exerts a bathochromic effect on the 233-nm band of the thiazole and shields both C-2H and C-5 H (0.67 and 0.89 ppm) (289). 

Williamson reaction is the synthesis of ethers by action of heat on a mixture of alkyl haldie and sodium or potassium alkoxide... 

Not long thereafter, Tarnowski and Cram reported the first example of a hinged bis-crown ether. The compound was prepared in the usual Williamson reaction by heating a mixture of 2,2, 3,3 -tetrahydroxy-l, r-binaphthyl with pentaethylene glycol ditosylate and KOH in aqueous THF solution. The product (mp 159.5—161°) shown in Eq. (3.30) was obtained in 30% yield. This compound was shown to complex bis-ammonium cations of several varieties . 

Methoxythiophene and 3-cyanothiophene have been prepared from 3-bromothiophene by means of a cupric oxide-catalyzed Williamson synthesis and by reaction with cuprous cyanide in quinoline, respectively. 

The first examples of alkylation reactions in molten salts were reported in the 1950 s. Baddeley and Williamson performed a number of intramolecular cycliza-tion reactions [76] (Scheme 5.1-46), carried out in mixtures of sodium chloride and aluminium chloride. The reactions were run at below the melting point of the pure salt, and it is presumed that the mixture of reagents acts to lower the melting point. 

Xie W., Yu L., Chen D., Li J., Ramirez J., Miranda N. F., Wang P. G. Lanthanide-Catalyzed Organic Synthesis in Protic Solvents in Green Chem. 1998 129, Ed.Anasts P. T. and Williamson T. C., Pb. Oxford Un. Press, Oxford Keywords aza-Diels-Alder reactions, rare earth metals... 

The chain mechanism is complicated when two hydrocarbons are oxidized simultaneously. Russell and Williamson [1,2] performed the first experiments on the co-oxidation of hydrocarbons with ethers. The theory of these reactions is close to that for the reaction of free radical copolymerization [3] and was developed by several researchers [4-9], When one hydrocarbon R H is oxidized in the liquid phase at a sufficiently high dioxygen pressure chain propagation is limited only by one reaction, namely, R OO + R H. For the co-oxidation of two hydrocarbons R1 and R2H, four propagation reactions are important, viz,... 

EM-values for the formation of cyclophane and naphthalenophane diethers by intramolecular Williamson reaction (51a) in 99% Me2SO at 25°C ... 

Williamson, D.H. Knighton, W.B. Grimsrud, E.P. Effect of Buffer Gas Alterations on the Thermal Electron Attachment and Detachment Reactions of Azu-lene by Pulsed High Pressure Mass Spectrometry. Int. J. Mass Spectrom. 2000, 795/796,481-489. 

Such an operation represents, in the synthetic sense, the classical Williamson reaction (or its r/j/o-equivalent in the case of sulphur). However, with amines, in order to avoid polyalkylations, a FGA must be carried out beforehand, introducing a carbonyl group (=0) at the p.ro-position, and proceeding then to the ipso-disconnection to afford the amine and an acyl derivative -as an acid chloride, for instance-, since in the synthetic direction monoacylations can be easily controlled owing to the deactivation of the resulting amide, which prevents further acylations. In practice, the amide can then be reduced by UAIH4. As an alternative solution, a... 

In a new method of ring enlargement of oxiranes to oxetanes, the intramolecular Williamson reaction is the essential last step. Reaction of an oxirane with selenomethyl-lithium reagents, followed by bromination, gives y-bromo alcohols, which can be cyclized by base to oxetanes. Since the oxiranes can be prepared readily from ketones and the selenomethyllithium reagent, this is also a synthesis of oxetanes from ketones (80TL585). 

A rapid one-pot method for converting 1,3-diols into oxetanes by the intramolecular Williamson reaction has recently been described. The monolithium salt is generated by treatment of the diol with one equivalent of butyllithium in cold THF, followed by addition of one equivalent of tosyl chloride to give a monotosylate, which is cyclized by addition of a second equivalent of butyllithium (equation 83). Yields of 70-90% are reported for a variety of alkyl- and aryl-substituted oxetanes (81S550). Another simple method for converting 1,3-diols into oxetanes consists of converting them to cyclic carbonate esters by ester... 

Thioethers (sulfides) can be prepared by treatment of alkyl halides with salts of thiols (thiolate ions).7S2 R may be alkyl or aryl. As in 0-35, RX cannot be a tertiary halide, and sulfuric and sulfonic esters can be used instead of halides. As in the Williamson reaction (0-12), yields are improved by phase-transfer catalysis.753 Instead of RS ions, thiols themselves can be used, if the reaction is run in benzene in the presence of DBU (p. 1023).754 Neopentyl bromide was converted to Me3CCH2SPh in good yield by treatment with PhS in liquid NH3 at -33°C under the influence of light.755 This probably takes place by an SrnI mechanism (see p. 648). Vinylic sulfides can be prepared by treating vinylic bromides with PhS in the presence of a nickel complex,756 and with R3SnPh in the presence of Pd(PPh3)4.757 R can be tertiary if an alcohol is the substrate, e.g,758... 

Ether synthesis. A variation of the Williamson reaction involves conversion of an alcohol to the thallium(I) alkoxide followed by alkylation. In practice the method is not useful for simple alcohols because the thallium alkoxide is very sparingly soluble in C6H6 or CH3CN. The method is useful however for substrates containing an additional oxygen function such as OH, OR, COOR, and CONR2 (listed in the order of effectiveness). It is particularly useful for alkylation of chiral hydroxyl groups, since it is free from racemizalion. 

The reaction between acetaldehyde and peracetic acid in the presence of copper or with no metal acetate present was studied by the method of Bawn and Williamson (4) using Methods I and II (see below) for determining peracetic acid and total peroxide, respectively. 

The kinetics of the noncatalytic reaction were studied by the method of Bawn and Williamson (4). They found 3.3-3.7 moles/liter for the equilibrium constant for the formation of the intermediate acetaldehyde monoperacetate (AMP) and a first-order rate constant for the decomposition of this intermediate to acetic acid of 0.015 min."1 at 25°C. We found difficulty in reproducing our results probably caused mainly by the high values of the blanks in the iodometric methods used. However, as an average of four determinations we obtained 0.03 min."1 at 30°C. 

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