Replacement with alkoxyl

If alkyl or aryl radicals at the silicon atom should be replaced with alkoxyl or aroxyl, tetraethoxysilane is re-etherified with triethanolamine in the presence of alcohols or phenols. 

Fluorine replacement by alkoxyl may also be achieved with free alcohol in the presence of a rhodium(in) catalyst (equations 4 and 5) [6, 7] or a chromium(VI) complex [, 0] (equation 5). 

Arylthio but not 2-arylthio groups in quinazolines can be replaced with hydroxide ion or alkylamines. 4-Alkylthio-2-alkyl (or aryl)-quinazolines are readily alkoxylated (65°, 1 hr, 80-90% yield) at the 4-position. Arylthio and alkylthio groups have been found to be poorer leaving groups than chloro in several azines. 

Alkoxylation (65°, 8 hr, 50% yields) and add-catalyzed 7-anilina-tion (50% yields) of 7-chloro-2-methyl-4-oxoquinoline have been described. Phenylhydrazine (in ethanolic HCl, 78°, 30 min, 80% yield) gives 7-substitution of 7-chloro-4-phenylhydrazinoquino-line. ° Preparative replacements (with CN, NH2, OH) are reported for 8-chloroquinoline. 

Electrolysis of a-sulfenyl carboxylic acids in protic solvents gives ketones, presumably via replacement of the carboxyl group with alkoxyl or acetoxyl groups and a subsequent two-electron oxidation of the sulfenyl moiety [Eq. (32)]. (This discussion is postponed to Sec. IV.D.)... 

Toxicity. While many new materials are added to the adhesive chemist s arsenal, some are being removed as well. Compounds which cause health and environmental concern include ethylenimine, methylene-fcw(o-chloroan-iline) (MOCA), hexamethylene diisocyanate, formaldehyde. Some systems are no longer in use in others, modifications have been made. Thus radiation-curing technology is replacing some types of multifunctional acrylate monomers with alkoxylated compounds, because the latter are less irritating and less toxic. An example is trimethylolpropane triethoxy triacrylate. 

Brewster et al. [72,73] reported the development of clear cosmetic sticks using Plutonic polyols. These sticks were used to deliver deodorant, antiperspirants, lipstick, etc. The authors indicated current products could be harsh to the skin when formulated with soaps, but attempts to reduce harshness by replacing the soap with alkoxylated fatty alcohols reduced the desired clarity of the sticks. The use of Plutonic F-127 and F-108 at approximately 4% of the formulation produced a stick with both clarity and rigidity, and was also mild to the skin. 

More useful than the preceding methods is cleavage of alkoxides by acetyl chloride or bromide. One, two, three, or four alkoxyls can be replaced by chloride or bromide. Benzoyl chloride gives poor yields, however. The tri- and tetrachlorides, which are stronger Lewis acids than mono- and dichlorides, coordinate with the alkyl acetate formed and yield distillable complexes (46,55,56). 

Heating TCNE with an alcohol in the presence of a mild base such as urea causes replacement of either one (19) or two (20) cyano groups by alkoxyl. The products with ethanol are 1-ethoxy-1,2,2-tricyanoethylene [69155-32-4] and l,l-bisethoxy-2,2-dicyanoethylene [17618-65-4]. 

Alkoxyl tion. The nucleophilic replacement of an aromatic halogen atom by an alkoxy group is an important process, especially for production of methoxy-containing iatermediates. Alkoxylation is preferred to alkylation of the phenol wherever possible, and typically iavolves the iateraction of a chloro compound, activated by a nitro group, with the appropriate alcohol ia the presence of alkaU. Careful control of alkaU concentration and temperature are essential, and formation of by-product azoxy compounds is avoided by passiag air through the reaction mixture (21). 

Chloroquinoline (401) reacts well with potassium fluoride in dimethylsulfone while its monocyclic analog 2-chloropyridine does not. Greater reactivity of derivatives of the bicyclic azine is evident also from the kinetic data (Table X, p. 336). 2-Chloroquinoline is alkoxylated by brief heating with methanolic methoxide or ethano-lic potassium hydroxide and is converted in very high yield into the thioether by trituration with thiocresol (20°, few hrs). It also reacts with active methylene carbanions (45-100% yield). The less reactive 3-halogen can be replaced under vigorous conditions (160°, aqueous ammonia-copper sulfate), as used for 3-bromoquino-line or its iV-oxide. 4-Chloroquinoline (406) is substituted by alcoholic hydrazine hydrate (80°, < 8 hr, 20% yield) and by methanolic methoxide (140°, < 3 hr, > 90% yield). This apparent reversal of the relative reactivity does not appear to be reliable in the face of the kinetic data (Tables X and XI, pp. 336 and 338) and the other qualitative comparisons presented here. 

Frequently the configuration of the hydroxyamino acid component of the peptide alkaloid could be deduced with the aid of NMR studies. The coupling constants, JaB, of several a-amino-j8-hydroxyamino acids as well as their A,iV-dimethyl derivatives and their methyl ethers were determined by Marchand et al. (34). They showed that only the N,N-dimethyl derivatives yielded JaB values of configurational significance and that the conversion of the hydroxyl to alkoxyl exerted virtually no influence. The Ja0 value of Ar,A-dimethyl-j3(p-tolyloxy)leucine in the threo form was 8.5 Hz whereas that in the erythro form was 2.5 Hz. Wenkert et al. studied frangulanine (10), discarine-A (6), and discarine-B (7) whose amide protons had been replaced by deuterium (22). The a- and jS-methine signals of hydroxyleucine occurred at 84,40 and 4.77, respectively, as a doublet with JaB = 8 Hz and as a double... 

In the case of mixed alkyl aryl esters the iodosilane reacts almost exclusively with the alkyl group. Similarly in the case of mixed alkyl silyl esters, the alkoxyl group is replaced by iodine. 

Scheme 1.2 Treatment of fluorinated tubes tized alkyl- and alkoxyl-nanotubes and amino-with strong nucleophiles and replacement of functionalized nanotubes as products, the fluorine substituents, leading to deriva-...

When halogenated phenols or phenolic ethers are nitrated with nitric acid a halogen o- or p- to hydroxyl or alkoxyl group can also be replaced. The ease of replacement appears to be in the order Cl< Br[Pg.128]

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