Alkoxyl

Typical auxochromes are hydroxyl, alkoxyl and aroxyl, amino, alkyl-amino and arylamino, all of which promote conjugation with lone pairs on oxygen or nitrogen atoms. 

In MeOH, l,4-dimethoxy-2-cyclohexene (379) is obtainejl from 1,3-cydo-hexadiene[315]. Acetoxylation and the intramolecular alkoxylation took place in the synthesis of the naturally occurring tetrahydrofuran derivative 380 and is another example of the selective introduction of different nucleo-philes[316]. In intramolecular 1,4-oxyacetoxylation to form the fused tetrahy-drofurans and tetrahydropyrans 381, cis addition takes place in the presence of a catalytic amount of LiCI, whereas the trans product is obtained in its absence[317]. The stereocontrolled oxaspirocyclization proceeds to afford the Irons product 382 in the presence of Li2C03 and the cis product in the presence of LiCl[ 318,319]. 

Reaction with Carbon Nucleophiles. Unactivated a2iddines react with the lithium salts of malonates or p-keto esters in the presence of lithium salts to yield 3-substituted pyttohdinones (56—59), where R = alkyl and aryl, and R = alkoxyl, alkyl, and aryl. 

Ethyleneimine reacts with epoxides to form hydroxyaLkylated products, eg, A/-(P-hydroxyethyla2iridine) [1072-52-2]. The epoxide component is frequentiy used in substoichiometric amount in order to prevent multiple aLkoxylation (180—190). Ethyleneimine and episulftdes react to give complex product mixtures, since the l-(2-mercaptoethyl)a2iridine produced initially can easily react further with both reactants (191,192). 

It is usually postulated that the final product in the accepted mechanism, the alkoxyl radical (4), cleaves (eqs. 14 and 15) before or after hydrogen abstraction, and that this accounts for the drop in molecular weight of the... 

Halogenated intermediates, dibromoneopentyl glycol [3296-90-0] (DBNPG), and alkoxylated derivatives of tetrabromobisphenol A are used extensively in flame-retardant apphcations. Similar properties can be derived from halogenated dibasic acids, chlorendic anhydride [115-27-5] (CAN), and tetrabromophthahc anhydride [632-79-1] (TBPA). Processes can be used to produce brominated products by the in situ bromination of polymers derived from tetrahydrophthahc anhydride. 

Halogenated intermediates based on chlorendic anhydride and alkoxylated, brominated bisphenol are quite stable and are used extensively in flame-retarded high temperature compositions, but brominated aUcychcs, such as dibromotetrahydrophthahc resin, are rapidly dehydrohalogenated at lower temperatures. 

KTB and KTA are superior to alkaU metal hydrides for deprotonation reactions because of the good solubiUties, and because no hydrogen is produced or oil residue left upon reaction. Furthermore, reactions of KTA and KTB can be performed in hydrocarbon solvents as sometimes requited for mild and nonpolar reaction conditions. Potassium alkoxides are used in large quantities for addition, esterification, transesterification, isomerization, and alkoxylation reactions. 

Organic Reagents. Amine oxides are used ia synthetic organic chemistry ia the preparation of olefins, or phase-transfer catalysts (47), ia alkoxylation reactions (48), ia polymerization, and as oxidizing agents (49,50). 

Alkoxylation. Ethoxylation of toluenediamines proceeds easily. Typical conditions are 90 to 120°C at pressures up to 500 kPa (72.5 psi) using a basic catalyst, eg, potassium hydroxide (13). 

TDA-derived polyols are made by alkoxylation. Polypropylene oxide adducts of I DA (14) and TDA-initiated polyether polyols (13,15) are used in rigid polyurethane foams and continue to be included in new formulations (62) as well as older appHcations. 

Etherification. Ethers of amyl alcohols have been prepared by reaction with ben2hydrol (63), activated aromatic haUdes (64), dehydration-addition reactions (65), addition to olefins (66—71), alkoxylation with olefin oxides (72,73) and displacement reactions involving thek alkah metal salts (74—76). 

Higher alkoxylated products, ie, oligomers, are formed by secondary reaction of oxide and the hydroxy group of the previous product. 

Hydrogen Sulfide andMercaptans. Hydrogen sulfide and propylene oxide react to produce l-mercapto-2-propanol and bis(2-hydroxypropyl) sulfide (69,70). Reaction of the epoxide with mercaptans yields 1-aLkylthio- or l-arylthio-2-propanol when basic catalysis is used (71). Acid catalysts produce a mixture of primary and secondary hydroxy products, but ia low yield (72). Suitable catalysts iaclude sodium hydroxide, sodium salts of the mercaptan, tetraaLkylammonium hydroxide, acidic 2eohtes, and sodium salts of an alkoxylated alcohol or mercaptan (26,69,70,73,74). 

Propylene oxide has found use in the preparation of polyether polyols from recycled poly(ethylene terephthalate) (264), haUde removal from amine salts via halohydrin formation (265), preparation of flame retardants (266), alkoxylation of amines (267,268), modification of catalysts (269), and preparation of cellulose ethers (270,271). 

The versatility of lithium aluminum hydride permits synthesis of alkyl, alkenyl, and arylsilanes. Silanes containing functional groups, such as chloro, amino, and alkoxyl in the organic substituents, can also be prepared. Mixed compounds containing both SiCl and SiH cannot be prepared from organopolyhalosilanes using lithium aluminum hydride. Reduction is invariably complete. 

Propoxylates, ethoxylates, and mixed alkoxylates of aUphatic alcohols or alkyl phenols are sulfated for use in specialty appHcations. 

Oxygen-Cont iiningAmines. This group includes amine oxides, ethoxylated alkylamines, l-(2-hydroxyethyl)-2-imidazolines, and alkoxylates of ethylenediamine. Oxygen-containing amines are steadily increasing in economic importance. 

Ethylenediamine Alkoxylates. The reaction 1,2-alkylene oxides with ethylenediamine forms the basis of a series of surfactants of the following general stmcture ... 

The partially alkoxylated chlorotitanates, (RO) TiCl, can be prepared in high purity by reaction of TiCl with an organosilane ester, Si(OR)4 (see Silicon compounds). The degree of esterification of the titanium can be controlled by the amount of silane ester used. When is 3 or 4, the addition of the appropriate alcohol and an amine receptor is required (5). 

Reactions with Alcohols. The tendency of titanium(IV) to reach coordination number six accounts for the rapid exchange of alkoxy groups with alcohols. Departure of an alkoxy group with the proton is the first step in the ultimate exchange of all four alkoxyls. The four-coordinated monomer is expected to react... 

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) ... 

Alkoxylation Ethylene and/or propylene oxides Alkoxylated castor oils... 

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). 

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