Williamson condensation

A second possibility to attach the chromophores to the polymer backbone is the polymer analogue modification with the appropriate electron or hole transporting unit. Complete substitution of poly(p-acetoxystyrene) was achieved through Williamson condensation with chloromethylstilbene resulting in a polymer with Mn = 22,000 Da, Mw/Mn = 2.1 and rg = 71 °C (Scheme 35 [96]). 

D. L. Williamson, Chemical Synthesis Under High Pressure Shock Loading, in Shock Waves in Condensed Matter (edited by Y.M. Gupta), Plenum, New York, 1986, pp. 693-711. 

Macrocycles have been prepared by formation of macrocyclic imines as well as by using variations of the Williamson ether synthesis ". Typically, a diamine or dialdehyde is treated with its counterpart to yield the Schiff s base. The saturated macrocycle may then be obtained by simple reduction, using sodium borohydride, for example. The cyclization may be metal-ion templated. In the special case of the all-nitrogen macrd-cycle, 15, the condensation of diamine with glyoxal shown in Eq. (4.14), was unsuccess-ful ... 

Williamson, A.D, Smith, W.B. "A Dilution Sampling System for Condensation Aerosol Measurements Design Specifications," Southern Research Institute, Special Report //SORI-EAS-79-793, 1979. 

A series of azophenol acerands 4 was prepared by condensation of crowned benzoquinones 10 with 2,4-dinitrophenylhydrazine in ethanol [7b], The quinone was derived from p-methoxyphenol (6) as shown in Scheme 1 [8]. By bis(hy-droxymethylation) (67% yield of 6, followed by methylation (92%) of the phenol group and Williamson-type reaction with ditosylates of oligoethyleneglycol in the presence of sodium hydride, crowned 1,4-dimethoxybenzene 9 was obtained in reasonable yields. Oxidative demethylation of 9 with ceric ammonium nitrate (CAN) in aqueous acetonitrile at 50 °C gave the desired crowned benzoquinones 10 in good yields. 

Treatments based on condensation reactions (such as in the classical Williamson synthesis) produce the most stable cotton derivatives. On the other hand, treatments based on addition reactions (such as in the Michael reaction) yield cellulose ethers that are somewhat less stable. This lower level of stability is because of the equilibrium nature of the addition reaction. Typical examples of these two types of cellulose etherification are carboxymethyla-tion [9,329,330] and cyanoethylation [9,329,330,332], respectively, both of which proceed in the presence of alkali. 

In the presence of sodium hydroxide, thiols react with alkyl halides to form the sulfides (20) the reaction occurs via the sodium thiolate and is analogous to the well-known Williamson synthesis of ethers and can also be applied to obtain unsymmetrical sulfides (Scheme 18). Symmetrical sulfides may be prepared directly by condensation of sodium sulfide with alkyl halides (Scheme 18). These reactions are of the SN2 type, and consequently the optimum yields of sulfides are realised using primary alkyl halides. 

R.J. Tucci, and T.G. Williamson Naturally occurring 222 radon daughters in tobacco and smoke condensate 1978 20A29. 

Bromodiphenylmethane may be prepared by the direet bromination of diphenylmethane which is then condensed with tropine, through the Williamson ether synthesis (making use of sodium alkoxide derivative of tropine), to yield the benztropine base. This is dissolved in an appropriate solvent and precipitated by treating it with an equimolar quantity of methanesulphonie aeid. 

The cement is first manufactured by reacting the 2,2-Bis-(p-hydroxyphenyl)propane and epichlorohydrin in the presence of base to form the condensation polymer. In this Williamson synthesis, the chlorine anion acts as a leaving group and the phenoxide anion is the nucleophile. This reaction, like any displacement is facilitated by the... 

The original preparatitm of aromatic polysulfraies was described in 1958 [110]. This was followed by investigations of many different structures of polysulfones. One current commercial material is a condensation product of 2,2 bisfhydroxyphenyl) propane with 4,4 -bis(chlorophenyl) sulfone. It forms by a Williamson synthesis, because the reactivity of the halogens is enhanced by the sulfone groups [47] ... 

Ba(OH)2 is known to cattdyze several base-catalyzed organic reactions in the solid form, Of the reactions, aldol condensation is the most common. In recent years, several organic reactions besides aldol condensation have been found to be effectively catalyzed by Ba(OH)2. These reactions are the Claisen-Schmidt reaction, esterification of acid chlorides, Williamson s ether synthesis, benzil-benzilic acid rearrangement, the synthesis of A -pyrazolines by the reaction of a,/3-unsaturated ketone with PhNHNHz Wittig-Homer reaction, and Michael addition. For these reactions, the Ba(OH)2 catalyst prepared from Ba(0H)2-8H20 by cidcination at 473 K shows the highest activity. 

Butylation of phenylacetonitrile with aqueous NaOH, as shown in Scheme 25, proceeds faster by use of high DF (>0.5) anion exchange resins.The strongly alkaline conditions degrade the quaternary ammonium ions of the catalyst. Catalyst (64) (1% DVB) is active for alkylation of phenylacetonitrile and benzyl phenyl ketone, and for Williamson ether synthesis, and it is much more stable in base than AERs. AERs in OH form are catalysts for dichlorocyclopropane syntheses from alkenes, chloroform and solid sodium hydroxide, and for dehydration of amides to nitriles. AERs in the appropriate hydroxide, acetate, or cyanide form are catalysts for aldol condensations, Michael reactions, Knoevenagel condensations, cyanoethylations and cyanohydrin syntheses. " ... 

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