Replacement alkoxyl

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). 

Alkoxy fluorides are prepared using acetyl fluoride. Alternatively, antimony trifluoride can be used to replace one alkoxyl by fluorine (58) ... 

Although a C—CN bond is normally strong, one or two cyano groups in TCNE can be replaced easily, about as easily as the one in an acyl cyanide. The replacing group can be hydroxyl, alkoxyl, amino, or a nucleophilic aryl group. Thus hydrolysis of TCNE under neutral or mildly acidic conditions leads to tricyanoethenol [27062-39-17, a strong acid isolated only in the form of salts (18). 

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). 

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). 

The versatility of pyrimidine substituted chloroquinazolines as intermediates is due to the ready replacement of the halogen atoms by hydrogen, alkyl, alkoxyl, amino, and mercapto groups (see Section VI, A). 

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. 

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. 

Every time a hydroxyl substitutent is replaced by an alkoxyl, a correction of 0.66 is added °° this is based on the increments observed for H3PO4 and its mono and dialkyl esters. 

A secondary reaction yields at the same time phenol ether by the replacement of the diazonium group by alkoxyl. This is clearly analogous to the conversion of diazonium salts to phenols. 

Slightly more than a mole of aluminum fer/.-butoxide is used for each mole of water split out as the alkoxide loses its effectiveness after the replacement of one alkoxyl by an hydroxyl group. 

From the determination of the molecular refractions of a large number of organic compounds containing tervalent arsenic, the atomic refraction of arsenic in each compound has been calculated,10 the values obtained varying from 9-2 to 14-39. Hydrogen, chlorine and alkyl groups in an arsine exert about the same influence on the atomic refraction of arsenic, but replacement of any of these by aryl groups causes an increase in the atomic refraction. The opposite effect results from substitution by a cyanide, oxalate or alkoxyl radical. 

In fluorinated lsooyamde dihalides and lmidoyl halides the halogens are replaced by alkoxyls [19 20, 21] (equation 18)... 

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-...

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. 

The halogen atom of quaternary salts of 3- and 5-halogeno-l-phenylpyrazoles may be replaced easily at 80-100° by hydroxyl, alkoxyl, sulfhydryl, thioalkyl, amino, alkylamino, dialkylamino, arylamino, or cyano groups.565,675-683 The chlorine atom of quaternary salts of N-substituted 5-chloropyrazoIes may be replaced by bromine541,550,579,684,685 or by iodine265,550, 662,684-887 by heating... 

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]

Acid chlorides and esters are derivatives of carboxylic acids. In such acid derivatives, the —OH group of a carboxylic acid is replaced by other electron-withdrawing groups. In acid chlorides, the hydroxyl group of the acid is replaced by a chlorine atom. In esters, the hydroxyl group is replaced by an alkoxyl (—O—R) group. 

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